Plasma arginine esterase in cystic fibrosis: kinetics of activation, identification as plasma kallikrein, reaction with alpha 2-macroglobulin and comparison with levels in normal plasma.

Abstract

Treatment of normal plasma with chloroform and ellagic acid yielded esterase activity against tosylarginine methyl ester, which reached a maximum within 2 h. After 2 h most or all of the activity as resistant to inhibition by soybean trypsin inhibitor (STI), but was still sensitive to the low molecular weight inhibitors di-isopropyl fluorophosphate, aprotinin and prolyl-phenylalanyl-arginyl chloromethane. The activity ran in gel chromatography with alpha 2 macroglobulin (ampha 2M), as if it were due to an alpha 2M proteinase complex. The generation of the arginine esterase activity by chloroform and ellagic acid was apparently dependent on the activation of factor XII, being blocked by Polybrene. In plasma pretreated with methylamine-HCl (an inactivator of alpha 2M), the arginine esterase was 95% sensitive to inhibition by STI. With regard to substrate specificity, inhibition characteristics, and gel chromatographic behaviour, it was indistinguishable from plasma kallikrein (EC 3.4.21.34, formerly 3.4.21.8). The chloroform and ellagic acid treatment of plasma resulted in a disappearance of prokallikrein simultaneous with the appearance of the arginine esterase. By these criteria, the arginine esterase activity was attributable entirely to plasma kallikrein either in its free form (methylamine-treated plasma) or bound to alpha 2M (buffer-treated plasma). Comparisons of STI-sensitive and STI-resistant arginine esterase activities of plasma samples from cystic fibrosis patients, obligate heterozyotes or other groups showed no significant differences in levels of activity, kinetics of activation or gel chromatographic behaviour. We conclude that cystic fibrosis is unrelated to any abnormality in plasma arginine esterase activity, contrary to some previous reports.