Cobalt ions yeast

Some coenzymes serve as biosynthetic precursors that afford structural parts of other coenzymes. Thus, the benzenoid moiety of the flavocoenzyme FMN serves as a precursor for the lower ligand 26 of the central cobalt ion in vitamin B12 (20) (Fig. 3) (5). Pyridoxal and NAD are used as precursors for the biosynthesis of thiamine in yeast (Fig. 4) (23, 24). 

Muscle aldolase is strongly inhibited by traces of heavy metals and its activity is not decreased by metal binding reagents such as cysteine and a,a -dipyridyl. Yeast aldolase, which has been extensively purified by Warburg, is inactivated by cysteine and reactivated by ferrous, zinc, or cobaltous ion. Aldolase of Clostridium perfringens, on the other hand, is reactivated by ferrous or cobaltous ions in the presence of cysteine. Pea aldolase is not inhibited by heavy metals nor by cysteine and is not activated by ferrous or cobaltous ions. It is puzzling that although each of these aldolases catalyzes the same thermodynamic reaction, they still possess markedly different activation requirements. 

Metals are used not only as labels in histochemistry and immunochemistry, but also for studying protein structure and properties. Some metal ions can serve as valuable probes by replacing the original ions in different metaloenzymes or other metaloproteins. For instance, cobalt can replace zinc on the active side of carboxy-peptidase, aldolase, carbonic anhydrase, phosphatase or yeast alcohol dehydrogena. ... 

Other Zinc Enzymes. Studies aimed at elucidating the mechanism of dimeric alcohol dehydrogenase enzymes have also been reported. Cobalt(n) can replace zinc(ii) at the two catalytic and non-catalytic sites in the liver enzyme, LADH. Reduction of pyridinealdehyde derivatives by the yeast enzyme has been examined. In acetonitrile solution, reduction by NADH analogues is catalysed by metal ions and mechanistic studies of the reaction have been carried out. Biomimetic studies of zinc-catalysed carbonyl reduction have also been reported. ... 

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