NEET PG Medical – 2019 – Question – 42
Glutamine is Increase in CSF, blood and urine, this is due to deficiency of
a) CPS-I
b) Arginase
c) OTC
d) Argininosuccinate synthetase
Correct Answer – A
Answer: A. CPS-I
CPS I deficiency is one of the proximal urea cycle defects and is due to a complete or partial deficiency of the mitochondrial enzyme carbamyl phosphate synthetase I (CPS I) which produces carbamyl phosphate from ammonia, ATP, and HCO3.
Carbamoyl phosphate synthetase I (CPS1 or CPSI) transfers an ammonia molecule from glutamine or glutamate to a molecule of bicarbonate that has been phosphorylated by a molecule of ATP.
The resulting carbamate is then phosphorylated with another molecule of ATP. The resulting molecule of carbamoyl phosphate leaves the enzyme.
CPS-I is the rate limiting (pacemaker) enzyme this pathway.
CPS-I is active only in the presence of N-Acetyl Glutamate, an allosteric activator.
