SEMIAUTOMATED MICROTITER PLATE ASSAY FOR MONITORING PEPTIDYLPROLYL CIS TRANS ISOMERASE ACTIVITY IN NORMAL AND PATHOLOGICAL HUMAN SERA/

An UV/VIS spectrophotometric assay technique was developed that was ab le to routinely monitor peptidyl-prolyl cis/trans isomerase (PPIase) a ctivity of biological fluids in 96-well microtiter plates. The assay, based on monitoring the cis-to-trans isomerization of succinyl-Phe-cis Pro-Phe-4-nitroanilide as substrate in a chymotrypsin-coupled reaction , yields a throughput of 96 samples per 30 min. The assay's capacity w as exemplified by dealing with the PPIase activity in several normal a nd pathological human sera. Reference values of 151 healthy subjects ( 83 females, 69 males, 17 to 60 years old) were found to possess signif icant sex-specific differences. PPIase activity factor K of the sera w as significantly greater in males (5th, 50th, 95th percentiles: 17, 36 , 55 K) than females (14, 30, 48 K). PPIase activities of sera from he althy donors (n = 151) were significantly higher (Maun-Whitney rank-su m test P < 0.0001) than those of patients (n = 47). PPIase activity in serum samples stored at 4 degrees C was stable for at least 20 h.