Increased sensitivity of lymphocyte Δ¹pyrroline-5- carboxylate reductase to inhibition by proline with transformation

THE mitogen-induced transformation of resting lymphocytes to proliferating blast forms is associated with a marked increase in amino-acid uptake ¹, protein synthesis² and enzyme activities³. There is little information, however, on the effect of transformation on enzymes of amino-acid metabolism. We therefore examined the biosynthetic and degradative enzymes of the non-essential amino acid, proline⁴, in resting and transformed lymphocytes. We found a selective increase of proline bio-synthetic enzymes in association with transformation. It is interesting that transformation also produced qualitative changes in Δ¹- pyrroline-5-carboxylate reductase, the enzyme which catalyses the committed step in proline synthesis.