Statistical calculations with the software CSS:STATISTICA (StatSoft) were used to analyze the relation between laboratory variables and PPIase activity, and to determine the standard deviation of kinetic constants.
We assayed PPIase activities in a pooled serum probe for six tetrapeptides and a tripeptide substrate.
An oligopeptide containing a prolyl bond, where the cis conformer is used as a substrate in any protease-coupled PPIase assay, consists of a mixture of two conformers, cis and trans, in solution [2,22-261.
A condition for quantifying PPIase activities from time courses of coupled reactions by applying the first-order rate law is a relation between substrate concentration [S] and Michaelis constant (KM) of [S] << [K.
To consider the influence of the proteolytic peptidylprolyl fragment, which is produced in large amounts in the fast phase of the coupled reaction, we investigated the influence of succinyl-Ala-Ala-Pro-Phe-OH on the PPIase activity of a mixture of 10 sera and in a separate experiment with purified Cyp18 and FKBP12.
Chymotrypsin is the protease used most frequently in PPIase assays, followed by subtilisin or thrombin [3,31].
We measured the PPIase activity in serum after preincubation of eight different serum samples with chymotrypsin at 5[degrees]C.
1, which describes the PPIase activity in the sample cell as arbitrary units.
Up to a twofold increase of PPIase activity was observed in serum samples not separated from blood clot after 8 h.
The PPIase activity patterns of the 151 healthy adult volunteers and the 47 patients (Fig.
A statistically significant correlation between PPIase activity and age was not detected.
Remarkably, all correlations (Pearson product-moment correlation) between any of these laboratory variables and PPIase activity were inverse (data not shown) but not statistically significant.