{PDOC00149}
{PS00165; DEHYDRATASE_SER_THR}
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* Serine/threonine dehydratases pyridoxal-phosphate attachment site  *
**********************************************************************

Serine and threonine  dehydratases [1,2]  are  functionally  and  structurally
related pyridoxal-phosphate dependent enzymes:

 - L-serine dehydratase (EC 4.2.1.13) and D-serine  dehydratase  (EC 4.2.1.14)
   catalyze the dehydratation of L-serine (respectively D-serine) into ammonia
   and pyruvate.
 - Threonine dehydratase  (EC 4.2.1.16) (TDH) catalyzes  the  dehydratation of
   threonine into  alpha-ketobutarate  and  ammonia.  In Escherichia coli  and
   other microorganisms,  two  classes  of  TDH  are  known  to  exist. One is
   involved in  the  biosynthesis of isoleucine, the other in hydroxamino acid
   catabolism.

Threonine synthase  (EC 4.2.99.2) is  also  a pyridoxal-phosphate  enzyme,  it
catalyzes the  transformation of  homoserine-phosphate into threonine.  It has
been shown [3] that  threonine  synthase  is  distantly related to the serine/
threonine dehydratases.

In all these enzymes, the pyridoxal-phosphate group is  attached  to a  lysine
residue.  The sequence around  this residue is sufficiently conserved to allow
the derivation  of  a  pattern  specific  to serine/threonine dehydratases and
threonine synthases.

-Consensus pattern: [DESH]-x(4,5)-[STVG]-x-[AS]-[FYI]-K-[DLIFSA]-[RVMF]-[GA]-
                    [LIVMGA]
                    [The K is the pyridoxal-P attachment site]
-Sequences known to belong to this class detected by the pattern: ALL.
-Other sequence(s) detected in SWISS-PROT: 12.

-Note: some   bacterial L-serine dehydratases - such as those from Escherichia
 coli - are iron-sulfur proteins [4] and do not belong to this family.

-Last update: November 1995 / Pattern and text revised.

[ 1] Ogawa H., Gomi T., Konishi K., Date T., Naakashima H., Nose K.,
     Matsuda Y., Peraino C., Pitot H.C., Fujioka M.
     J. Biol. Chem. 264:15818-15823(1989).
[ 2] Datta P., Goss T.J., Omnaas J.R., Patil R.V.
     Proc. Natl. Acad. Sci. U.S.A. 84:393-397(1987).
[ 3] Parsot C.
     EMBO J. 5:3013-3019(1986).
[ 4] Grabowski R., Hofmeister A.E.M., Buckel W.
     Trends Biochem. Sci. 18:297-300(1993).

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