Pigeon liver diacetyl reductase kinetic and thermodynamic studies with NADH as coenzyme

Abstract

1. 1.The dependence of the initial rate of the reaction catalyzed by pigeon liver diacetyl reductase on the concentration of substrates (diacetyl and NADH) and the product (acetoin and NAD +) inhibition pattern are consistent with both a rapid equilibrium random Bi-Bi mechanism with two dead-end ternary complexes and a Theorell-Chance one. 2. 2.The inhibition patterns with acetone and pentane-3-one (competitive for diacetyl and uncompetitive for NADH) discard the random Bi-Bi mechanism and prove that the reaction follows that of Theorell-Chance with NADH as the leading substrate. 3. 3. K m diacetyl (3.1 mM), K m NADNl (100 μM), K s diacetyl (5 mM), K s NADH (162 μM), activation energy (13.8 kcal/mole), ΔH* (13.3 kcal/mole), ΔF* (14.5 kcal/mole) and ΔS* (= −4 cal/mole per degree) were estimated.