{PDOC00700}
{PS00901; CYS_SYNTHASE}
{BEGIN}
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* Cysteine synthase/cystathionine beta-synthase P-phosphate attachment site *
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Cysteine synthase (EC 2.5.1.47) (CSase) is the pyridoxal-phosphate dependent
enzyme responsible [1] for the formation of cysteine from O-acetyl-serine and
hydrogen sulfide with the concomitant release of acetic acid. In bacteria such
as Escherichia coli, two forms of the enzyme are known (genes cysK and cysM).
In plants there are also two forms, one located in the cytoplasm and the other
in chloroplasts.
Cystathionine beta-synthase (EC 4.2.1.22) [2] catalyzes the first irreversible
step in homocysteine transulfuration; the conjugation of homocysteine and
serine forming cystathionine. Like Csase it is a pyridoxal-phosphate dependent
enzyme.
The two types of enzymes are evolutionary related. The pyridoxal-phosphate
group of CSases has been shown to be attached to a lysine residue which is
located in the N-terminal section of these enzymes; the sequence around this
residue is highly conserved and can be used as a signature pattern to detect
this class of enzymes.
-Consensus pattern: K-x-E-x(3,4)-[PAF]-[STAGC]-x-S-[IVAPM]-K-x-R-x-[STAG]-
x(2)-[LIVM]
[The second 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: NONE.
-Last update: April 2006 / Pattern revised.
[ 1] Saito K., Kurosawa M., Murakoshi I.
"Determination of a functional lysine residue of a plant cysteine
synthase by site-directed mutagenesis, and the molecular evolutionary
implications."
FEBS Lett. 328:111-114(1993).
PubMed=8344414
[ 2] Swaroop M., Bradley K., Ohura T., Tahara T., Roper M.D.,
Rosenberg L.E., Kraus J.P.
"Rat cystathionine beta-synthase. Gene organization and alternative
splicing."
J. Biol. Chem. 267:11455-11461(1992).
PubMed=1597473
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