Open AccessNADH‐Dependent Glutamate Synthase from Lupin Nodules
Author(s) -
BOLAND Michael J.
Publication year - 1981
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1981.tb06228.x
Subject(s) - glutamate synthase , atp synthase , glutamate receptor , biology , biochemistry , chemistry , enzyme , glutamate dehydrogenase , receptor
3‐Acetylpyridine‐adenine dinucleotide, reduced form (AcPdADH) is able to act as an alternative reductant in glutamate‐synthase‐catalysed glutamate synthesis. In the AcPdADH‐dependent reaction, k cat and K m values for the other substrates are fourfold lower than those for the NADH‐dependent reaction, and K m for AcPdADH is about 3 μM. AcPdADH acts as a competitive inhibitor with respect to NADH in NADH‐dependent glutamate synthesis, with a K i of 1 fμM. Glutamate synthase catalyses NADH‐dependent reduction of AcPdAD + . This appears to proceed by a substituted‐enzyme (ping‐pong) mechanism, with competitive substrate inhibition by NADH at high levels. The K m value for this reaction are 1.4 μM for NADH and 14 μM for ACPdAD + and k cat , is 51 s − ; K 1 for NADH is about 10 μM. The latter findings suggest that NADH is capable of reducing the enzyme molecule in the absence of other substrates and that a reduced form of the enzyme can exist in the absence of bound NADH.