Structural and mechanistic analysis of two refined crystal structures of the pyridoxal phosphate-dependent enzyme dialkylglycine decarboxylase.
Aaslestad, H. G. (Louisiana State University, Baton Rouge), and A. D. Larson. Bacterial metabolism of 2-methylalanine. J. Bacteriol. 88:1296-1303. 1964.-A bacterium isolated from soil was found to oxidize 2-methylalanine to 65% of the theoretical value by an adaptive enzyme system. Manometric experiments with whole cells indicated that acetone but not isopropylamine was an intermediate. Cellular extracts produced carbon dioxide from 2-methylalanine when pyruvate was added to the reaction mixture. Dialysis stimulated the 2-methylalanine metabolizing system, providing pyridoxal phosphate and pyruvate were supplied. A study of the stoichiometry of this pyridoxal phosphate-dependent reaction indicated that acetone and carbon dioxide were principal products. The formation of carbon dioxide from 2-methylalanine seemed dependent upon transfer of the amino group to pyridoxal phosphate. Other 2-methyl amino acids were found to be decarboxylated by this system, thus indicating a lack of absolute specificity.