Studies on DOPA Transaminase of Alcaligenes faecalis

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Some enzymatic properties were examined on the transaminase (DOPA transaminase) which catalyzes the reaction between 3, 4-dihydroxyphenyl pyruvate (DOPP) and certain amino acids to form 3, 4-dihydroxyphenyl-L-alanine (DOPA). The cell-free extract from Alcaligenes faecalis IAM 1015 was used as the DOPA transaminase. L-Aspartate, L-gluta-mate, and L-phenylalanine were utilized efficiently as amino donor. The occurrence of three kinds of transaminase-apartate-DOPP transaminase (ADT), glutamate-DOPP transaminase (GDT), and phenylalanine-DOPP transaminase (PDT)-was postulated.
The pH optima of these enzymes were observed in the alkaline pH range. The enzymes were unstable in the acidic range and inactivated above 60°C. Ca²⁺, Mg²⁺, and Mn²⁺ protected PDT from heat denaturation. Fe²⁺, Cu²⁺, and Al³⁺ remarkably inhibited the enzyme reaction.