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PyridoxaL 5'-Phosphate Dependent Enzymes class IV (PLPDE_IV). This D-amino acid superfamily, one of five classes of PLPDE, consists of branched-chain amino acid aminotransferases (BCAT), D-amino acid transferases (DAAT), and 4-amino-4-deoxychorismate lyases (ADCL). BCAT catalyzes the reversible transamination reaction between the L-branched-chain amino and alpha-keto acids. DAAT catalyzes the synthesis of D-glutamic acid and D-alanine, and ADCL converts 4-amino-4-deoxychorismate to p-aminobenzoate and pyruvate. Except for a few enzymes, i. e., Escherichia coli and Salmonella BCATs, which are homohexamers arranged as a double trimer, the class IV PLPDEs are homodimers. Homodimer formation is required for catalytic activity.
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