Aminotransferases share certain mechanistic features with other pyridoxal-phosphate dependent enzymes, such as the covalent binding of the pyridoxal-phosphate group to a lysine residue. On the basis of sequence similarity,
these various enzymes can be grouped [1,2] into subfamilies. One of these,
called class-V, currently consists of the following enzymes:
Phosphoserine aminotransferase (EC 18.104.22.168), an enzyme which catalyzes the
reversible interconversion of phosphoserine and 2-oxoglutarate to
3-phosphonooxypyruvate and glutamate. It is required both in the major
phosphorylated pathway of serine biosynthesis and in pyridoxine
biosynthesis. The bacterial enzyme (gene serC) is highly similar to a
rabbit endometrial progesterone-induced protein (EPIP), which is probably a
phosphoserine aminotransferase .
Serine--glyoxylate aminotransferase (EC 22.214.171.124) (SGAT) (gene sgaA) from
Serine--pyruvate aminotransferase (EC 126.96.36.199). This enzyme also acts as
an alanine--glyoxylate aminotransferase (EC 188.8.131.52). In vertebrates, it
is located in the peroxisomes and/or mitochondria.
Isopenicillin N epimerase (gene cefD). This enzyme is involved in the
biosynthesis of cephalosporin antibiotics and catalyzes the reversible
isomerization of isopenicillin N and penicillin N.
NifS, a protein of the nitrogen fixation operon of some bacteria and
cyanobacteria. The exact function of nifS is not yet known. A highly
similar protein has been found in fungi (gene NFS1 or SPL1).
The small subunit of cyanobacterial soluble hydrogenase (EC 1.12.-.-).
Hypothetical protein ycbU from Bacillus subtilis.
Hypothetical protein YFL030w from yeast.
The sequence around the pyridoxal-phosphate attachment site of this class of
enzyme is sufficiently conserved to allow the creation of a specific pattern.
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