Glutamate dehydrogenase (EC –4) fromPeptostreptococcus asacch-arolyticushas a strong preference for NADH over NADPH as a coenzyme, over 1000-fold in terms ofkcat ⁄Kmvalues. Sequence alignments across the wider family of NAD(P)-dependent dehydrogenases might suggest that this preference is mainly due to a negatively charged glutamate at position 243 (E243) in the adenine ribose-binding pocket.