DATABASE CLONING HUMAN DELTA(1)-PYRROLINE-5-CARBOXYLATE SYNTHETASE (P5CS) CDNA - A BIFUNCTIONAL ENZYME CATALZING THE FIRST 2 STEPS IN PROLINE SYNTHESIS

Delta(1)-pyrroline-5-carboxylate synthetase (P5CS) catalyzes the ATP a nd the NAD(P)H-dependent conversion of L-glutamate to glutamic gamma-s emialdehyde (GSA) which is the metabolic precursor for proline biosynt hesis. We cloned a human P5CS cDNA by database cloning strategy and se quenced 2,907 bp from this cDNA which has a closed open reading frame (ORF) of 2,385 bp coding for a polypeptide of 795 amino acid residues. This cDNA, as its plant counterpart encodes a bifunctional enzyme, wi th both gamma-glutamyl kinase (gamma-GK) and gamma-glutamyl phosphate reductase (gamma-GPR) activities that catalyzes the first 2 steps in p roline biosynthesis and it hybridizes to a 4.5 kb mRNA from various ti ssues. A human genetic disease caused by a deficient P5CS has been rec ognized. The phenotypic features for deficiency of P5CS include joint hyperlaxity, skin in hyperelasticity, cataract and mental retardation with hyperammonemia and low plasma levels of proline, citrulline and o rnithine.