Thomas Hartmann

Der Tryptophanabbau bei Endomycopsis Vernalis und Anderen Hefen

Summary1.The degradation of tryptophan (Try) and some of its potential intermediates has been studied in Endomycopsis vernalis. The following degradation products were identified in surface-cultures of Endomycopsis which had been fed with C-14-labeled d,l-Try for 12–24 hrs: β-(indolyl-3)-pyruvic acid (IBS); β-(indolyl-3-)lactic acid (IMS); α-(indolyl-3-)acetic acid (IES); indolyl-3-carboxylic acid (ICS); β-(indolyl-3-)ethanol (β-IÄ); indole-3-aldehyde (IAld); Nα-acetyl-tryptophan (Ac-Try). Indole-3-acetaldehyde (IAAld) could be demonstrated only in experiments in which cell-free extracts were used.2.IMS was isolated from the culture medium and was identified by means of chemical methods and IR- and mass-spectra. Feeding of both d- and l-Try yielded L-(-)-indolyllactic acid exclusively.3.The first step in the breakdown of Try has been shown to be a transamination-reaction leading to the formation of IBS. The NH2-group can be transferred to α-ketoglutaric acid as well as to phenylpyruvic acid.4.The degradation products of Try were determined quantitatively by feeding C-14-(3-alanyl-)d,l-Try to Endomycopsis cultures. After 10 hrs nearly 60% of the original radioactivity of Try was found in IMS. In comparison to IMS the concentrations of the other degradation products formed were rather small: Ac-Try (about 1/7 of the IMS-concentration), IES (1/10), β-IÄ (1/12), ICS (1/80), IAld (1/220).5.The following pathways in the degradation of Try in Endomycopsis vernalis are assumed to be of physiological, i.e., enzymatic, nature: Try→IBS→IAAld→β-IÄ, and Try→Ac-Try, and IBS→IMS. IMS and β-IÄ appear to be metabolic end products.Zusammenfassung1.Nach Verfütterung von d,l-Tryptophan (d,l-Try) und anderen Indolkörpern an Oberflächenkulturen von Endomycopsis vernalis konnten folgende Abbauprodukte nachgewiesen werden: Nα-Acetyl-tryptophan (Ac-Try), β-(Indolyl-3-)brenztraubensäure (IBS), β-(Indolyl-3-) milchsäure (IMS), α-(Indolyl-3-)essigsäure (IES), Indol-3-carbonsäure (ICS), β-(Indolyl-3-)äthanol (β-IÄ), Indol-3-aldehyd (IAld). Der Nachweis von Indolyl-3-acetaldehyd (IAAld) gelang nur in Versuchen mit zellfreien Extrakten.2.IMS wurde präparativ isoliert und mit Hilfe chemischer und physikalischer Methoden identifiziert. Sowohl die Verfütterung von d- als auch von l-Try lieferten ausschließlich l-(-)-Indolylmilchsäure.3.Der erste Schritt im Try-Abban ist eine Transaminierung, die zur Bildung von IBS führt. Die NH2-Gruppe kann sowohl auf α-Ketoglutarsäure als auch auf Phenylbrenztraubensäure übertragen werden.4.Eine quantitative Bestimmung der Try-Abbauprodukte mit Hilfe von 14C(3-Alanyl)-d,l-Try ergab, daß der überwiegende Teil des Try zu IMS abgebaut wird. Es folgen in abnehmendem Mengenverhältnis: Ac-Try, IES, β-IÄ, ICS, IAld.5.Auf Grund der Ergebnisse wird angenommen, daß folgende Reaktionen im Try-Abbau bei Endomycopsis physiologisch, d.h. enzymatisch bedingt sind: Try→IBS→IAAld→β-IÄ sowie Try→Ac-Try und IBS→IMS.1. The degradation of tryptophan (Try) and some of its potential intermediates has been studied in Endomycopsis vernalis. The following degradation products were identified in surface-cultures of Endomycopsis which had been fed with C-14-labeled D,L-Try for 12-24 hrs: β-(indolyl-3)-pyruvic acid (IBS); β-(indolyl-3-)lactic acid (IMS); α-(indolyl-3-)acetic acid (IES); indolyl-3-carboxylic acid (ICS); β-(indolyl-3-)ethanol (β-IÄ); indole-3-aldehyde (IAld); Nα-acetyl-tryptophan (Ac-Try). Indole-3-acetaldehyde (IAAld) could be demonstrated only in experiments in which cell-free extracts were used. 2. IMS was isolated from the culture medium and was identified by means of chemical methods and IR- and mass-spectra. Feeding of both D- and L-Try yielded L-(-)-indolyllactic acid exclusively. 3. The first step in the breakdown of Try has been shown to be a transamination-reaction leading to the formation of IBS. The NH2-group can be transferred to α-ketoglutaric acid as well as to phenylpyruvic acid. 4. The degradation products of Try were determined quantitatively by feeding C-14-(3-alanyl-) D,L-Try to Endomycopsis cultures. After 10 hrs nearly 60% of the original radioactivity of Try was found in IMS. In comparison to IMS the concentrations of the other degradation products formed were rather small: Ac-Try (about 1/7 of the IMS-concentration), IES (1/10), β-IÄ (1/12), ICS (1/80), IAld (1/220). 5. The following pathways in the degradation of Try in Endomycopsis vernalis are assumed to be of physiological, i.e., enzymatic, nature: Try→IBS→IAAld→β-IÄ, and Try→Ac-Try, and IBS→IMS. IMS and β-IÄ appear to be metabolic end products.

Organspezifische multiple Formen der Glutamatdehydrogenase in Medicago sativa

SummaryThe alteration of the multiple forms of NAD-dependent glutamic dehydrogenase (GDH) during the development of Medicago sativa is investigated by means of polyacrylamide electrophoresis. Seed germination is accompanied by a characteristic change of the GDH-isoenzyme pattern. Seeds contain seven isoenzymes, which gradually decrease in number during germination. At the same time a pattern of new isoenzymes becomes visible. The seed pattern is called GDH-I and the later appearing pattern GDH-II. GDH-I is characteristic for the cotyledons, whereas GDH-II is the typical pattern of the root system. Shoots produce a mixed pattern composed of the GDH-II isoenzymes as well as some GDH-I isoenzymes.These isoenzyme patterns are organ specific. No qualitative change occurs during further development of the plants and during growth in the presence of different inorganic and organic N-sources in the culture medium.All the individual isoenzymes are found predominantly in the particulate fraction. They represent stable forms which are not altered by variation of the conditions of enzyme extraction or during enzyme purification. Re-electrophoresis of the individual isoenzymes following elution from the polyacrylamide gels reveals only one specific band. The molecular weights of all the distinctive isoenzymes are identical.There is some evidence that the different isoenzymes represent conformational forms of one enzyme, and it is postulated that the GDH-I isoenzymes are correlated to a normal metabolic (or catabolic) function of the enzyme, whereas the GDH-II isoenzymes are responsible for a primarily anabolic function of glutamic dehydrogenase.

Properties of glutamate dehydrogenase from Lemna minor

Abstract Sterile cultures of Lemna minor grown in the presence of either nitrate, ammonium or amino acids failed to show significant changes in glutamate dehydrogenase (GDH) levels in response to nitrogen source. Crude and partially purified GDH preparations exhibit NADH and NADPH dependent activities. The ratio of these activities remain ca 12:1 during various treatments. Mixed substrate and product inhibition studies as well as electrophoretic behaviour suggest the existence of a single enzyme which is active in the presence of both coenzymes. GDH activity was found to be localized mainly in mitochondria. Kinetic studies revealed normal Michaelis kinetics with most substrates but showed deviations with NADPH and glutamate. A Hill-coefficient of 1.9 determined with NADPH indicates positive cooperative interactions, whereas a Hill-coefficient of 0.75 found with glutamate may be interpreted in terms of negative cooperative interactions. NADH dependent activity decreases rapidly during gel filtration whereas the NAD + and NADPH activities remain unchanged. GDH preparations which have been pretreated with EDTA show almost complete loss of NADH and NAD + activities. NADPH activity again remains unaffected. NAD + activity is fully restored by adding Ca 2+ or Mg 2+ , whereas the NADH activity can only be recovered by Ca 2+ but not at all by Mg 2+ . Moderate inhibition of GDH reactions observed with various adenylates are fully reversed by adding Ca 2+ , indicating that the adenylate inhibition is due solely to the chelating properties of these compounds.

Der Tryptophanabbau bei Rhizobium leguminosarum

SummaryThe degradation of tryptophan (Try) and some of its potential intermediates has been studied in nodule bacteria (Rhizobium leguminosarum Frank, ATCC 10324). In feeding experiments with washed suspensions the following degradation products of Try could be identified by thin-layer chromatography: indolyl-3-pyruvic acid (IBS); indolyl-3-acetic acid (IES); β-(indolyl-3)-lactic acid (IMS); indole-carboxylic acid-(3) (ICS); β-(indolyl-3)-ethanol (β-IÄ); indole-aldehyde-(3) (IAld); indolyl-3-acetaldehyde (IAAld); Nα-acetyl-tryptophan (Ac-Try).An active Try-transaminase leading to the formation of IBS has been demonstrated. Phenylpyruvic acid as well as α-ketoglutaric acid served as amino group acceptors.The breakdown of Try was followed quantitatively by using C-14(2-alanyl-)D,L-tryptophan. After 16 hrs nearly 16% of the original radioactivity was found in the ether-extractable material. IES and IMS were formed in much the highest concentrations.Indole-3-acetonitrile (IAN), although not a Try-metabolite in Rhizobium leguminosarum was converted to IES via indole-3-acetamide (IAAm). The following physiological pathways in the breakdown of Try in Rhizobium leguminosarum have been confirmed: Try → Ac-Try and IBS; IBS → IAAld; IAAld → β-IÄ and IES; no further degradation of IES was observed.

Methode zur Quantitativen Trennung und Bestimmung Flüchtiger Pflanzlicher Amine

Summary1.A routine method for the separation and determination of volatile primary and secondary amines found in biological material is described.2.Amine concentrations up to 10 μM were converted quantitatively (error <2%) to the corresponding 2,4-dinitrophenyl derivatives (DNP-amines) by means of 2,4-dinitrofluorobenzene (DNFB). The DNP-amines were extrated with ether and determined spectrophotometrically at 350 mμ for DNP-derivatives of primary amines and at 264 mμ for DNP-derivatives of secondary amines. Procedures for the preparation of DNP-amine test substances, their absorption spectra and their extinction coefficients are given.3.The quantitative separation of DNP-amines was carried out on paper chromatograms pretreated with 5% paraffin, using a methanol-water solvent saturated with chloroform.4.The quantitative recovery of volatile amines from biological material was accomplished by an extraction with hot 0.01N HCl and alkaline steam distillation.5.Experiments with test mixtures and biological extracts showed that the entire method is quantitative and reproducible with an error less than 5% for the following plant amines: methylamine, ethylamine, n- and iso-propylamine, isobutylamine, n-hexylamine and dimethylamine.Zusammenfassung1.Es wurde eine Methode ausgearbeitet, mit der sich kleine Mengen flüchtiger primärer und sekundärer Amine in Form ihrer 2,4-Dinitrophenylderivate (DNP-Amine) papierchromatographisch quantitativ bestimmen lassen.2.Die Präparation von DNP-Amintestsubstanzen wird beschrieben, Absorptionsspektren, Eichkurven und Extinktionskoeffizienten der DNP-Amine werden angegeben. Die spektralphotometrischen Messungen wurden bei den für die einzelnen DNP-Amine ermittelten Wellenlängen maximaler Absorption durchgeführt: DNP-Derivate primärer Amine= 350 nm, DNP-Dimethylamin=369 nm, 2,4-Dinitranilin=236 nm.3.Zur Umsetzung von Aminkonzentrationen bis zu 10 μMol mit 2,4-Dinitrofluorbenzol (DNFB) und zur Ätherextraktion der gebildeten DNP-Amine wurde ein einfaches für Reihenuntersuchungen geeignetes quantitatives Verfahren entwickelt. Das Verfahren ist mit einem Fehler von <±2% gut reproduzierbar.4.Zur quantitativen Papierchromatographie der DNP-Amine erwies sich als unbewegliche Phase mit 5% Paraffin/Petroläther imprägniertes Papier, als Fließmittel Chloroform/Methanol/Wasser (4/10/6) als am besten geeignet. Zur Elution der DNP-Amine aus dem Papierchromatogramm wurde Methanol verwendet.5.Zur quantitativen Gewinnung flüchtiger Amine aus biologischem Material erwies sich nach Vorextraktion mit kochender 0,01 n HCl die alkalische Wasserdampfdestillation für Methyl-, Dimethyl-, n+i-Propyl-, i-Butyl, i-Amyl-und n-Hexylamin als geeignet. Lediglich β-Phenyläthylamin ließ sich durch Destillation nicht verlustfrei gewinnen.6.Reproduzierbarkeit und Fehlerbelastung der vollständigen Bestimmungsmethode (Wasserdampfdestillation, Umsetzung mit DNFB, Papierchromatographie, Elution und spektralphotometrische Bestimmung der DNP-Amine) wurden geprüft. Amintestsubstanzgemische ließen sich ebenso wie Aminextrakte aus biologischem Material (saprophytischen Kulturen von Claviceps purpurea) mit einem Fehler >±5% quantitativ bestimmen.

Translokation und biochemisches Verhalten von D- und L-Phenylalanin bei Vicia faba

SummaryD,L-Phenylalanine (phe) applied to the first primary leaf of a young Vicia faba plant moves into the sieve tubes and appears in the honey dew of aphids feeding on the third primary leaf. Ethanol extracts of the treated leaf contain labeled phe and an acidic compound which could be identified as N-malonyl-D-phe.D-phe-l-14C was obtained pure by enzymatic decarboxylation of the L-isomer of commercially available D,L-phe-l-14C, using an enzyme from red algae (Hartmann, 1967). The uptake of the D-isomer of phe by the sieve tubes is independent of the age of the treated leaf. L-phe applied to a young leaf is completely incorporated into protein; L-phe taken up by an older leaf is translocated in considerable amounts.Pulse-labeling with the two isomers shows that D-phe entering the sieve tube system is quickly removed to the parenchyma where it is acylated with malonic acid to the phloem immobile N-malonyl-D-phe. L-phe does not react with malonic acid at all. It is translocated to the centers of protein synthesis.

Über Das Zeitliche Auftreten flüchti ger amine und Freier Aminosäurenin Wachsenden, Saprophytischen Kulturen von Claviceps Purpurea

ummary1.Six strains of Claviceps purpurea were examined for their ability to form volatile amines in different saprophytic media. All strains produced predominantly iso-amylamine and n-hexylamine, whereas iso-butylamine propylamine, ethylamine and methylamine were formed in much smaller amounts. The different nutrient conditions influenced the amount, but not the kind of amine formed.2.In an amino acid-free culture medium, iso-amylamine and n-hexylamine were formed during the growth period, but not during the ensuing period of autolysis.3.Eighteen amino acids were identified by analyses of both mycelium and growth medium during the development of the culture. Alanine was found in much the highest concentrations followed by glutamic acid, serine, glycine, valine, leucine/iso-leucine, lysine, threonine, aspartic acid, asparagine, glutamine, proline and arginine. Phenylalanine, tyrosine, α-and γ-aminobutyric acid and α-aminoheptanoic acid were found in only small amounts.4.The relative concentrations of free amino acids varied only slightly during the growth period. However, the absolute quantities of amino acids increased during this period, whereas they decreased greatly during autolysis.5.The results are discussed particularly in relation to amine biogenesis in Claviceps purpurea.Zusammenfassung1.Sechs Claviceps purpurea-Stämme wurden saprophytisch unter verschiedenen Nährbedingungen auf ihre Fähigkeit zur Bildung flüchtiger Amine geprüft. Alle Stämme bildeten am stärksten i-Amylamin und n-Hexylamin, während Methyl-, Äthyl-, Propyl-und i-Butylamin im geringeren Konzentrationen, z.T. nur in Spuren, nachweisbar waren. Die unterschiedlichen Nährbedingungen beeinflußten die Aminbildung nur quantitativ nicht aber qualitativ.2.Die Bildung von i-Amyl-und n-Hexylamin wurde bei Claviceps purpurea-Stamm B 63 im Verlaufe der Kulturentwicklung quantitativ verfolgt. Dabei zeigte sich, daß diese Amine bevorzugt während des Mycelwachstums gebildet werden. Unter Autolysebedingungen konnte keine Aminbildung mehr beobachtet werden.3.Eine Analyse der freien Aminosäuren aus Mycel und Nährlösung von Claviceps purpurea-Stamm B 63 im Verlaufe der Kulturentwicklung erbrachte den Nachweis von 18 freien Aminosäuren. In weitaus höchsten Konzentrationen ließ sich Alanin nachweisen, in mittleren Konzentrationen folgten Glutaminsäure, Serin, Glycin, Valin, Leucin/Isoleucin und Lysin, während. Threonin, Asparaginsäure, Asparagin, Glutamin, Prolin, Arginin und eine nicht identifizierte Substanz in etwas geringeren, α-und γ-Aminobuttersäure, Phenylalanin und Tyrosin und α-Aminoheptansäure in sehr kleinen Mengen nachweisbar waren. Die qualitative und quantitative Zusammensetzung des Aminosäurespektrums aus Nährlösung und Mycel wies nur geringfügige Unterschiede auf und änderte sich im verlaufe des Kulturwachstums wenig. Unter Autolysebedingungen nahm die Aminosäuregesamtkonzentration stark ab.4.Die Versuchsergebnisse werden im Zusammenhang mit Untersuchungen zur Biogenese der Mutterkornamine diskutiert.

Über eine Valin-Carboxylyase aus Bacillus sphaericus

Summary1.The occurrence of a l-valine carboxy-lyase in Bacillus sphaericus has been demonstrated. The enzyme was found to occur in four out of nine strains tested.2.Some properties of the decarboxylase were studied in detail using acetonedried cells of B. sphaericus ATCC 245. The substrate-unspecific enzyme decarboxylates the following amino acids: valine, norvaline, leucine, 2-amino n-butyric acid, norleucine, isoleucine, methionine, alanine and phenylalanine. When two substrates are present simultaneously no additive effects are detected.3.The pH optimum for the reactions is about pH 7.7–7.9, the optimum temperature between 50 and 60°C.4.The enzyme is activated by pyridoxal phosphate (PLP) and, to a lower extent, by pyridoxal. In the absence of added PLP the rate of decarboxylation decreases continuously. The inactivation occurs more rapidly during decarboxylation of leucine than of valine; added leucine progressively inhibits valine decarboxylation.5.The decaroxylations are sensitive to reagents known to combine with carbonyl and — SH groups. PLP protects the enzyme to some extent against a progressive inhibition by iodoacetate which is stronger with leucine than with valine. It doesnt, however, reverse inactivation already established.6.The enzyme activity is highest in very young cultures of Bacillus sphaericus. It decreases rapidly in the early exponential phase of growth.Zusammenfassung1.In 4 von 9 untersuchten Stämmen von Bacillus sphaericus ließ sich eine l-Valin-Carboxylyase nachweisen.2.Einige Eigenschaften des Enzyms wurden an Acetonpräparaten von B. sphaericus ATCC 245 näher untersucht. Die Decarboxylase reagiert substratunspezifisch mit folgenden Aminosäuren: Valin, Norvalin, Leucin, 2-Amino-n-buttersäure, Norleucin, Isoleucin, Methionin, Alanin und Phenylalanin. Bei gleichzeitigem Angebot zweier Substrate läßt sich kein additiver Effekt feststellen.3.Das pH-Optimum der Enzymkatalyse liegt bei pH 7,7–7,9, das Temperaturoptimum zwischen 50 und 60°C.4.Die Decarboxylase wird durch Pyridoxalphosphat (PLP), in geringerem Maße auch durch Pyridoxal, aktiviert. Ohne Zusatz von PLP nimmt die Decarboxylierungsrate stetig ab, und zwar bei Leucin sehr viel schneller als bei Valin; die Decarboxylierung von Valin wird durch Leucin gehemmt.5.Carbonyl- und SH-Gruppenreagentien hemmen die Decarboxylase. PLP schützt das Enzym in gewissem Umfang gegen die bei Leucin stärker als bei Valin progressiv zunehmende Hemmung durch Jodacetat, kann aber eine bereits eingetretene Inaktivierung nicht wieder aufheben.6.Die Enzymaktivität ist am höchsten in ganz jungen Kulturen von Bacillus sphaericus; schon zu Beginn des exponentiellen Wachstums fällt sie steib ab.

Stofftransport in Rotalgen

SummaryLeucine-(U)-C14 applied to the midrib of a young phylloid of Delesseria sanguinea moves basipetally and acropetally and eventually appears in other phylloids of the same plant. The highest velocity of transport calculated was 63 cm/h. The pathway of movement seems to be the veins of the phylloids and the central core of the cauloid. Similar results had been obtained with Cystoclonium purpureum. Both algae belong to the Florideae with axial cells. Observations with the light microscope of veins of Delesseria revealed that the proposed conducting elements (up to 540 μm long) are interconnected by synapses having 1 to 4 “pit fields”, which occur as very thin parts of the wall. Single pit fields of the same structure occur in lateral walls, connecting two rows of conducting cells. The pit fields are mostly occluded by slime-like material staining yellow with iodine which is attached to one side of the synapsis. Conducting cells contain several nuclei and a small amount of threadlike, branched rhodoplasts; they are surrounded by starch cells. In cauloids which have overwintered, the starch cells are depleted of starch.Leucine-(U)-C(14) applied to the midrib of a young phylloid of Delesseria sanguinea moves basipetally and acropetally and eventually appears in other phylloids of the same plant. The highest velocity of transport calculated was 63 cm/h. The pathway of movement seems to be the veins of the phylloids and the central core of the cauloid. Similar results had been obtained with Cystoclonium purpureum. Both algae belong to the Florideae with axial cells. Observations with the light microscope of veins of Delesseria revealed that the proposed conducting elements (up to 540 μm long) are interconnected by synapses having 1 to 4 pit fields, which occur as very thin parts of the wall. Single pit fields of the same structure occur in lateral walls, connecting two rows of conducting cells. The pit fields are mostly occluded by slime-like material staining yellow with iodine which is attached to one side of the synapsis. Conducting cells contain several nuclei and a small amount of threadlike, branched rhodoplasts; they are surrounded by starch cells. In cauloids which have overwintered, the starch cells are depleted of starch.

Endogen und exogen ausgelöste Änderung des Isoenzymspektrums der NAD-spezifischen Glutamatdehydrogenase im Sproß von Pisum sativum

The isoenzymes of NAD-specific glutamic dehydrogenase (GDH) of Pisum sativum, separated by polyacrylamide gel electrophoresis, constitute two patterns, each of which covers seven individual isoenzymes. One pattern (GDH-I) is found in the cotyledons and young shoots. The second one (GDH-II) occurs together with at least some GDH-I isoenzymes in pea roots. In the shoots of older pea plants GDH-II isoenzymes become visible in addition to the GDH-I pattern.Section of the cotyledons (but not of the roots) of young pea seedlings causes the formation of the complete GDH-II isoenzyme pattern in the shoots within a few hours. It has been verified that the cotyledons specifically suppress the formation of the GDH-II pattern in the young shoot. In older plants which no longer depend on the cotyledons this effect is maintained somewhat less obviously by the root system.In experiments with isolated shoot segments or shoot tips it has been shown that NH 4 (+) reinforces the formation of the GDH-II whereas glucose shows the opposite effect.The formation of the GDH-II isoenzymes in the presence of NH 4 (+) is accompanied by an increase of the specific activity of GDH. Simultaneously the ratio of aminating activity (anabolic reaction) to deaminating activity (catabolic reaction) changes in favor of the anabolic reaction.The results support the supposition that the GDH-I and GDH-II isoenzyme patterns correspond to different molecular forms of one enzyme, the GDH-II representing a form with predominantly anabolic function and the GDH-I a form which has merely metabolic or catabolic function.SummaryThe isoenzymes of NAD-specific glutamic dehydrogenase (GDH) of Pisum sativum, separated by polyacrylamide gel electrophoresis, constitute two patterns, each of which covers seven individual isoenzymes. One pattern (GDH-I) is found in the cotyledons and young shoots. The second one (GDH-II) occurs together with at least some GDH-I isoenzymes in pea roots. In the shoots of older pea plants GDH-II isoenzymes become visible in addition to the GDH-I pattern.Section of the cotyledons (but not of the roots) of young pea seedlings causes the formation of the complete GDH-II isoenzyme pattern in the shoots within a few hours. It has been verified that the cotyledons specifically suppress the formation of the GDH-II pattern in the young shoot. In older plants which no longer depend on the cotyledons this effect is maintained somewhat less obviously by the root system.In experiments with isolated shoot segments or shoot tips it has been shown that NH4+reinforces the formation of the GDH-II whereas glucose shows the opposite effect.The formation of the GDH-II isoenzymes in the presence of NH4+is accompanied by an increase of the specific activity of GDH. Simultaneously the ratio of aminating activity (anabolic reaction) to deaminating activity (catabolic reaction) changes in favor of the anabolic reaction.The results support the supposition that the GDH-I and GDH-II isoenzyme patterns correspond to different molecular forms of one enzyme, the GDH-II representing a form with predominantly anabolic function and the GDH-I a form which has merely metabolic or catabolic function.