||Bast E, Hartmann T, Steiner M.
||[Studies on a valine carboxy-lyase of Bacillus sphaericus].
[Article in German]
||1. 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 doesn't, 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.