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* Malate dehydrogenase active site signature *
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Malate dehydrogenase (EC 1.1.1.37) (MDH)  [1,2] catalyzes  the interconversion
of malate to  oxaloacetate utilizing the NAD/NADH  cofactor system. The enzyme
participates in the citric acid cycle and exists in all aerobics organisms.

While prokaryotic organisms contains a single form of MDH, in eukaryotic cells
there are  two  isozymes: one which is located in the mitochondrial matrix and
the other in the cytoplasm.  Fungi  and  plants also harbor a glyoxysomal form
which  functions in the glyoxylate pathway. In plants chloroplast there is an
additional  NADP-dependent form of  MDH (EC 1.1.1.82)  which  is essential for
both the universal  C3 photosynthesis (Calvin)  cycle and the more specialized
C4 cycle.

As a signature pattern  for  this enzyme we have chosen a region that includes
two residues  involved in the catalytic mechanism [3]:  an aspartic acid which
is involved  in a  proton relay  mechanism,  and  an  arginine which binds the
substrate.

-Consensus pattern: [LIVM]-T-[TRKMN]-L-D-x(2)-R-[STA]-x(3)-[LIVMFY]
                    [D and R are the active site residues]
-Sequences known to belong to this class detected by the pattern: ALL,  except
 for MDH from  the archaebacteria  Methanothermus fervidus [4], whose sequence
 is very distantly related (if at all !) to that of other MDH.
-Other sequence(s) detected in SWISS-PROT: NONE.
-Last update: October 1993 / Pattern and text revised.

[ 1] McAlister-Henn L.
     Trends Biochem. Sci. 13:178-181(1988).
[ 2] Gietl C.
     Biochim. Biophys. Acta 1100:217-234(1992).
[ 3] Birktoft J.J., Rhodes G., Banaszak L.J.
     Biochemistry 28:6065-6081(1989).
[ 4] Honka E., Fabry S., Niermann T., Palm P., Hensel R.
     Eur. J. Biochem. 188:623-632(1990).