J. Michael Poston

METHYL‐VITAMIN B12 AS A SOURCE OF METHYL GROUPS FOR THE SYNTHESIS OF ACETATE BY CELL‐FREE EXTRACTS OF CLOSTRIDIUM THERMOACETICUM

Glucose fermentation by Clostridium themnoaceticum leads to the accumulation of nearly three moles of acetate per mole of substrate dec0mposed.l The possibility that one of the three moles of acetate is derived indirectly from carbon dioxide was suggested by the discovery of Barker and Kamen2 that acetate, labeled almost equally in both carbon atoms, is produced when glucose is fermented in the presence of added CI4O2. This possibility was later confirmed by Woods demonstration3 that nearly one-third of the acetate molecules produced during the dissimilation of glucose in the presence of C1302 is formed by a mechanism in which adjacent carbon atoms are derived from C1302. Thus, glucose fermentation by Cl. thermoaceticum is represented by the following overall reactions: CGH12O6 f 2H20 -+ ZCHBCOOH + 2CO2 + 8H ( 1 ) 8H + 2C02 + CH3COOH + 2H20 (2)

Biochemical effects of ischemia on isolated, perfused rat heart tissues☆

Isolated working rat hearts perfused with Krebs-Hensleit buffer were arrested and made ischemic. After 22 min, the hearts were reperfused with buffer, yielding restoration of function. Nucleotide levels rose and fell in the cardiac tissue as ischemia was imposed; the changes were consistent with the energy needs of the tissue. ATP concentrations in the tissues fell by 75% during ischemia, AMP levels were low initially and subsequently rose 5-fold, and ADP levels were essentially unchanged. Upon reperfusion ATP levels rebounded, although not to initial values, and AMP returned to initial values. During ischemia, there was a 10-fold or greater rise in inosine, hypoxanthine, and xanthine levels which fell to normally low levels upon reperfusion. Lactate dehydrogenase (LDH) activity rose during ischemia and returned to baseline upon reperfusion. Changes in LDH isozyme distribution suggest that, during ischemia, there is an increased proportion of liver-associated forms which returns to normally low levels upon reperfusion. Glutamate oxalacetate transaminase activity rose slightly at 5 min of ischemia, but, by 22 min of ischemia, it had fallen to 60% of initial values. Upon reperfusion, activity rose and, by 15 min, had reached 127% of initial values. On the other hand, there is no significant change in levels of extractable creatine kinase or isocitrate dehydrogenase activities as a result of the various conditions imposed on the hearts. As an index of protein oxidation, carbonyl levels in extractable protein rose during ischemia and were over four times the initial values at 5 min of reperfusion but, with continued reperfusion, declined to approximately 150% of initial values at 15 min.

Coenzyme B12-dependent enzymes in potatoes: Leucine 2,3-aminomutase and methylmalonyl-coa mutase

Abstract Extracts of potato tubers contain endogenous activities of two coenzyme B 12 -dependent enzymes, leucine 2,3-aminomutase and methylmalonyl-CoA mutase. These activities are stimulated by the addition of coenzyme B 12 and are inhibited by intrinsic factor. The inhibition is overcome by coenzyme B 12 .

[7] An anaerobic laboratory

Publisher Summary This chapter provides an overview of an anaerobic laboratory chamber. The chamber is a space of approximately 1400 cubic feet enclosed by a gas-tight partition. The gas-tight partition is made of 3/8 inch carbon steel plates supported on a framework of I-beams. All the floor plates are riveted to the concrete floor and all joints and seams are welded. Doors to the gas locks and the emergency doors are fabricated at the site from the same steel as the shell of the chamber. Placing the chamber in service once it is stocked with supplies and equipment is a relatively simple. Prior to closing the doors, the drain in the waste sink is filled with water. After checking the operation of the emergency system, the chamber is sealed and nitrogen is added through the purge valve. The chamber is vented at the other end of the N 2 circulation loop. After about an hour, the O 2 level is less than 0.5% oxygen-in-nitrogen. Access to the chamber is provided through the personnel lock in which the life-support mask is donned. Once the mask is tightly fitted to the face, the worker closes the outside door and the lock is purged. During this time the pressure within the chamber is raised close to its maximum to prevent the purge from driving oxygen through the door seals into the anaerobic room.

Distribution of leucine 2,3-aminomutase activity in various organs of the rat and in subcellular organelles of rat liver

Abstract Leucine 2,3-aminomutase, the cobalamine-dependent enzyme involved in the conversion of β-leucine to leucine, has been shown to be widely distributed in rat organs. The activity is highest in skeletal and cardiac muscle, lower in brain, liver, and kidney, and very low in small intestine. In rat liver, the activity is nearly all in the cytosolic fraction.

On the role of acetyl cyanide in the cyanide-induced acetylation of amino acids by enzymes of Clostridium kluyveri

Abstract Evidence has been obtained indicating that acetyl cyanide is an intermediary in the HCN-dependent acetylation of amino acids by acetyl phosphate that is catalyzed by cell-free extracts of Clostridium kluyveri. Acetyl cyanide formation from acetyl phosphate requires coenzyme A (CoA) and at least two enzymes present in C. kluyveri. One enzyme, phosphotransacetylase, catalyzes the formation of acetyl CoA from acetyl phosphate and CoA: the other enzyme catalyzes a reaction between acetyl CoA and HCN to form acetyl cyanide. In the absence of a suitable acetyl acceptor, the acetyl cyanide undergoes almost instantaneous, non-enzymic hydrolysis, but in the presence of aliphatic amines it reacts preferentially and non-enzymically to produce the N-acetyl derivatives. At relatively high concentrations of reactants, thiolesters undergo non-enzymic cleavage by HCN to form acetyl cyanide. The characteristics of the enzymic and non-enzymic cyanolytic reactions have been studied.

Pelczaria aurantia gen. nov., sp. nov., a newly described organge-colored bacterium

An organism from a goldfish aquarium, isolated on barbital medium, was found to be a Grampositive coccus which divided in alternating planes, often appearing as a doublet or as a tetrad with adjacent sides flattened. It grew well, although slowly, on rich solid medium (LB agar) and in liquid brain-heart infusion at room temperature (ca. 22°C); growth was slower and less extensive at 30°C or 37°C. No growth was seen at 4–5°C or at 42°C. It withstands brief exposure to ultraviolet radiation. Its growth was inhibited by low levels (0.1 unit/ml) of penicillin but was unaffected by levels of acetazolamide in excess of 1 mg/ml, indicating that it lacks carbonic anhydrase. Acid was not produced from glucose, maltose, mannose, lactose, or sucrose and only weakly, if at all, from fructose. Its DNA has a G+C mol percent of 59 measured chromatographically and neither the DNA nor rRNA from the organism hybridized with DNA from any organism that seemed related on morphological or other bases. Thin-layer chromatography of chloroform: methanol extracts of the organism show that it contains phosphatidyl choline, phosphatidyl ethanolamine, and phosphatidyl glycerol. Cell-wall preparations contain glutamic acid, serine, histidine, lysine, and alanine in the ratio of 1:1:1:1:8. Colonies were red-orange in color due, in larger measure, to a carotenoid tentatively identified as rhodopin. The organism was named Pelczaria aurantia.