Identification of a functional arginine residue involved in coenzyme binding by the NADP-specific glutamate dehydrogenase of Neurospora.

The NADP-specific glutamate dehydrogenase (EC 1.4.1.4) of Neurospora crassa is inhibited by reaction with 1,2-cyclohexanedione which binds to arginine residues. With the 14C-labeled reagent, a peptide was isolated with the sequence: Gly-Gly-Leu-Arg-Leu-His-Pro-Ser-Val-Asn-Leu, corresponding to residues 78 through 88 in the protein. The arginine, residue 81, was present as N7,N8-(1,2-dihydroxycyclohex-1,2-ylene)-arginyl (or DHCH-arginine). Present evidence indicates that this arginine residue resides at or near the nicotinamide binding domain of the enzyme. Similar sequences are present in the bovine liver enzyme (EC 1.4.1.3) and the NAD-specific glutamate dehydrogenase of Neurospora (EC 1.4.1.2).