Homotropic allosteric control in clostridial glutamate dehydrogenase: Different mechanisms for glutamate and NAD⁺?

Abstract

Clostridial glutamate dehydrogenase mutants with the 5 Trp residues in turn replaced by Phe showed the importance of Trp 64 and 449 in cooperativity with glutamate at pH 9. These mutants are examined here for their behaviour with NAD + at pH 7.0 and 9.0. The wild-type enzyme displays negative NAD + cooperativity at both pH values. At pH 7.0 W243F gives Michaelis-Menten kinetics, and the same behaviour is shown by W243F and also W310F at pH 9.0, but not by W64F or W449F. W243 and W310 are apparently much more important than W64 and W449 for the coenzyme negative cooperativity, implying that different conformational transitions are involved in cooperativity with the coenzyme and with glutamate.

Multiple Forms of Glutamate Dehydrogenase in Animals: Structural Determinants and Physiological Implications

“…[67], does not equate to a lack of allosteric regulation in these GDHs. Indeed, the GDHs from other kingdoms may be allosterically regulated by other elements of the protein structure [68,69,70]. …”

Structural Basis for Leucine-induced Allosteric Activation of Glutamate Dehydrogenase

“…N. crassa GDH is also activated by non-substrate di-or polycarboxylic acids, suggesting heterotropic regulation in this GDH. As for bacterial GDH, GDH from Clostridium symbiosum has been shown to be regulated in a homotropic manner (9). Recently, another type of GDH, GDH180, which is a very large GDH with N-and C-terminal extension domains, has been reported to be regulated heterotropically by amino acids: GDHs from Streptomyces clavuligerus (activated by aspartate and asparagine) (10), Janthinobacterium lividum (activated by aspartate and arginine) (11), and Pseudomonas aeruginosa (activated by arginine and inhibited by citrate) (12).…”

Hetero-oligomeric glutamate dehydrogenase from Thermus thermophilus

“…The N. crassa GDH is also activated by nonsubstrate, di-or polycarboxylic acids (West et al, 1967), suggesting heterotropic regulation in this GDH. As for bacterial GDH, GDH from Clostridium symbiosum has been known to be regulated in a homotropic manner (Hamza & Engel, 2008). Recently, heterotropic regulation has been reported for NAD + -dependent GDHs from bacteria such as Streptomyces clavuligerus (activation by AMP, aspartate and asparagine) (Miñambres et al, 2000), Janthinobacterium lividum (activation by aspartate and arginine) (Kawakami et al, 2007) and Pseudomonas aeruginosa (activation by arginine and inhibition by citrate) (Lu & Abdelal, 2001).…”