Akira Kanazawa

β-Aminoisobutyrate-α-ketoglutarate transaminase in relation to β-aminoisobutyric aciduria

Abstract β-Aminoisobutyrate-α-ketoglutarate transaminase described by Kupiecki and Coon was further purified from hog kidney. The enzyme catalyzed the transamination with its l isomer while the d isomer, the natural form, was practically inactive as the substrate. The activity of the enzyme in the kidney of an hereditary high excretor of β-aminoisobutyric acid was not different from the activities of the low excretors. These findings indicate that the enzyme is not the principle enzyme catalyzing the degradation of the amino acid in vivo, and suggest the occurrence of another enzyme reaction by which d -β-aminoisobutyric acid is metabolized.

Isolation of γ-l-glutamyl-l-glutamic acid and γ-l-glutamyl-l-glutamine from bovine brain

Abstract Two peptides have been isolated from 28.5 kg of bovine brains using a combination of ion-exchange chromatographic separations. They were identified as γ- l -glutamyl- l -glutamic acid and γ- l -glutamyl- l -glutamine. The synthesis of these peptides has been described.

Identification of γ-glutamylserine, γ-glutamylalanine, γ-glutamylvaline and S-methylglutathione of bovine brain

Abstract Three γ-glutamyl dipeptides and a γ-glutamyl tripeptide were purified from bovine brain by a combination of ion-exchange chromatogaphic techniques. These were identified as γ-glutamylserine, γ-glutamylalanine, γ-glutamylvaline and S -methylglutathione by acid hydrolysis, terminal amino acid determination and comparison of paper chromatographic and paper electrophoretic properties of the isolated compounds with those of synthetized peptides.

A METHOD OF DETERMINATION OF HOMOCARNOSINE AND ITS DISTRIBUTION IN MAMMALIAN TISSUES

HOMOCARNOSINE, y-aminobutyryl-L-histidine, which was isolated by PISANO, WILSON, COHEN, ABRAHAM and UDENFRIEND (1961), and later by KANAZAWA, KAKIMOTO, MIYAMOTO and SANO (1965), occurs in the central nervous system. ABRAHAM, PISANO and UDENFRIEND (1962) found this dipeptide in a higher concentration in the white matter of human brains. In our preliminary experiment (SHIMIZU, KAKIMOTO and SANO, 1966), however, the concentration of homocarnosine was higher in the thalamus, hypothalamus and cerebellum than the cerebral cortex, and the difference in the concentration between the grey and white matter was not clear in the human brain. This led us to re-examine the concentration of homocarnosine in various regions of the human brain as well as in the brains of different species of vertebrates. M E T H O D S

Isolation and identification of γ-l-glutamylglycine from bovine brain

A peptide has been isolated from 28.5 kg of bovine brains through ion-exchange chromatography, and identified as γ-l-glutamylglycine. The identification was based on elementary analysis, determination of amino acid sequence, infrared spectrum, paper chromatography, paper electrophoresis and determination of configuration of glutamyl residue by l-glutamic acid decarboxylase (EC 4.1.1.15). The synthesis of α- and γ-l-glutamylglycine are also described.

Metabolic effects of methionine in schizophrenic patients pretreated with a monoamine oxidase inhibitor.

ORAL administration of a large amount of methionine to schizophrenic patients who had been treated with a monoamine oxidase inhibitor (MAOI) was reported to produce psychic symptoms which have been interpreted either as an intensification of schizophrenic symptoms or as superimposed toxic symptoms1–4. The effects of methionine and MAOI have been explained as an increase in the amounts of methylated amines, such as bufotenin, N,N-dimethyltryptamine, 3,4-dimethoxyphenylethylamine or unknown amines which have been claimed to be psychotogenic substances. One of the purposes of the present experiments is to determine whether methionine increases the rates of N or O-methylation of catechol and indolic amines.

Isolation of γ-l-glutamyl-l-β-aminoisobutyric acid from bovine brain

Abstract 1. 1. A peptide has been isolated from bovine brains by a combination of ion-exchange chromatographic methods. Acid hydrolysis of the peptide yielded β-aminoisobutyric acid and l -glutamic acid. The l -configuration of the glutamic acid residue was determined enzymically. The results of elementary analysis were approximately in accord with those required for glutamyl-β-aminoisobutyric acid, the N-terminal group being glutamic acid. 2. 2. γ- l -Glutamyl- d -β-aminoisobutyric acid, γ- l -glutamyl- l -β-aminoisobutyric acid and α- l -glutamyl- d -β-aminoisobutyric acid were synthesized for comparison. The first two synthetic compounds, but not the last, behaved similarly on paper chromatography and paper electrophoresis to the isolated compound. 3. 3. The infrared spectrum of the isolated peptide was identical with that of γ- l -glutamyl- l -β-aminoisobutyric acid, but different from γ- l -glutamyl- d -β-aminoisobutyric acid. Melting point and solubility of the isolated compound were also similar to those of the former compound. The isolated compound was thus identified as γ- l -glutamyl- l -β-aminoisobutyric acid.

γ-Glutamylglutamine lactamase in mammalian tissues

Abstract An enzyme that catalyzes the degradation of γ- l glutamyl- l -glutamine to pyrrolidone carboxylic acid and glutamic acid has been purified I4-fold from an extract of acetone powder of rat liver. The substrate specificity of the enzyme preparation was examined on 9 γ-glutamyl peptides, 3α-glutamyl peptides, 4 dipeptides containing a glutamine residue in the carboxy terminal position, and 15 other compounds. Other properties of the enzyme are also described. This enzyme seems to be different from previously known peptidases and from γ-glutamyl lactamase, and is tentatively referred to as γ-glutamylglutamine lactamase. The distribution of the enzyme in various organs of the rat and guinea pig has been examined.

The distribution of γ-L-glutamyl-L-glutamine in mammalian tissues

This preliminary work therefore indicates that it is apparently possible to produce myelin in the central nervous system with a different lipid composition from that of the adult myelin sheath. It seems likely that the presence of desmosterol and the rclative lack of cerebroside is associated with the early stages of myelinogenesis. The isolated myelin fraction prepared from 12-day-old rats or from animals treated with triparanol may therefore represent a primitive type of myelin similar to that of the plasma membrane from which it is formed. Although myelin must be regarded as one of the most metabolically stable components of the body (DAVISON, 1964) our experiments on surviving rats suggest that desmosterol incorporated during development can slowly be replaced by cholesterol. It is possible that the early form of myelin undergoes later rearrangement to form adult, metabolically stable, myelin. This hypothesis is being tested and work on the metabolism and physical stability of early myelin is in progress.