A new nicotinamide–adenine dinucleotide-dependent hydroaromatic dehydrogenase of Lactobacillus plantarum and its role in formation of (-)t-3t-4-dihydroxycyclohexane-c-1-carboxylate

Abstract

1. A new induced NAD-dependent hydroaromatic dehydrogenase was isolated from a cell-free extract of Lactobacillus plantarum 13a and purified 175-fold. 2. The enzyme catalyses the oxidation of (-)-quinate, (-)-shikimate, (-)-dihydroshikimate and (-)t-3,t-4-dihydroxycyclohexane-c-1-carboxylate with NAD+, and the reverse action with NADH. 3. The Km values at the optimal pH10.0 for these substrates are 0.85, 0.75, 0.52 and 0.74mm respectively, and the corresponding values for NAD+ are 0.45, 0.26, 0.34 and 0.36mm respectively. 4. The stereochemical requirements of the enzyme and the role it may play in the reduction of (-)-quinate to (-)t-3,t-4-dihydroxycyclohexane-c-1-carboxylate are discussed and a pathway is suggested.