The amino-acid sequence similarity of plant glutamate dehydrogenase to the extremophilic archaeal enzyme conforms to its stress-related function.

A cDNA clone encoding grapevine (Vitis vinifera L. cv Sultanina) NAD(H)-glutamate dehydrogenase (GDH) was isolated from a cDNA expression library by immunoscreening with a polyclonal antibody raised against grapevine GDH. Nucleotide sequence analysis revealed an open reading frame (ORF) encoding a precursor protein of 411 amino acids (aa) with a calculated molecular mass of 44.517 kDa. The deduced aa sequence showed relatively higher homology to GDH from archaebacteria species, than to those from eukaryotes and eubacteria. This resemblance indicated a functional and/or evolutionary relationship in this class of enzymes which might be relevant to the stress-related function of plant GDH. We have shown that the bacterially produced plant GDH was thermostable.