sentences:  In solution, P5C is in spontaneous equilibrium with glutamate-5-semialdhyde (GSA).The stereoisomer ("S")-1-pyrroline-5-carboxylate (also referred to as L-P5C) is an intermediate metabolite in the biosynthesis and degradation of proline and arginine.In prokaryotic proline biosynthesis, GSA is synthesized from γ-glutamyl phosphate by the enzyme γ-glutamyl phosphate reductase.