The following dehydrogenases have been shown  to share regions of
Alanine dehydrogenase (EC 188.8.131.52), an enzyme which catalyzes the NAD-
dependent reversible reductive amination of pyruvate into alanine.
Pyridine nucleotide transhydrogenase (EC 184.108.40.206), which is the enzyme that
catalyzes the reduction of NADP+ to NADPH with the concomitant oxidation of
NADH to NAD+. This enzyme is located in the plasma membrane of prokaryotes
and in the inner membrane of the mitochondria of eukaryotes. The
transhydrogenation between NADH and NADP is coupled with the translocation
of a proton across the membrane. In prokaryotes the enzyme is composed of
two different subunits: an α chain (gene pntA) and a β chain (gene
pntB) while in eukaryotes it is a single chain protein.
The sequence of alanine dehydrogenase from several bacterial species are
related with those of the α subunit of bacterial pyridine nucleotide
transhydrogenase and of the N-terminal half of the eukaryotic enzyme. The two
most conserved regions correspond respectively to the N-terminal extremity of
these proteins and to a central glycine-rich region which is part of the
NAD(H)-binding site. We have developed signature patterns for both regions.
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