In vitro Colorimetric Method to Measure Plant Glutamate Dehydrogenase Enzyme Activity

Abstract

Glutamate dehydrogenase (GDH) is an NAD(H) dependent enzyme that catalyzes, in vitro, the reversible amination of glutamate. Here we describe how to determine spectrophotometrically GDH activity monitoring NADH evolution. This protocol is described here for Arabidopsis thaliana (A. thaliana) although it is also valid for other plant species. GDH protein is a hexamer composed, in the case of Arabidopsis, of a combination of GDHα, GDHβ and GDHγ subunits. Every combination of subunits is possible; however, it is still barely known whether different combinations affect the enzymatic properties of the hexamers. In other species, hexamers are a combination of GDHα and GDHβ but it cannot be discarded the existence of other genes since for instance GDHγ subunit in Arabidopsis was described in Fontaine et al. (2012).Glutamate + NAD+ + H+ → 2-Oxoglutarate + NADH + NH4+