Synthetic Substrate Assay Research Articles

Problems in the assay of thrombin using synthetic peptides as substrates

Synthetic tripeptides (code named S-2160 and Chromozym TH) have been used as substrates for the measurement of thrombin activity in two commercial preparations of bovine thrombin, using the International Standard for thrombin (I.S. thrombin) for comparison. The results, when compared to the data obtained using the natural substrate, fibrinogen, indicated the following: 1) the thrombin potency of one commercial thrombin was much higher using the synthetic substrate assays than when the clotting assay was used; the synthetic substrate data for the other commercial thrombin differed significantly from the clotting assay data but in a less consistent manner. 2) the loss of the biological activity of thrombin when stored in frozen aliquots (−20°C) was very rapid, while the amidolytic activity of similarly stored samples did not alter significantly. It was concluded that the synthetic substrates used in this study were of little use when measuring the biological activity of thrombin preparations in comparison to the established standard for thrombin (I.S. thrombin).

Peptidase in the cornea

Peptidase activity, operative at neutral pH, was found in bovine cornea and conjunctiva with a synthetic substrate assay. The same peptidase was found previously in commercial bacterial collagenase preparations. Cell fractionation of homogenates revealed the activity to be maximal in the high-speed supernatant of the corneal and conjunctival epithelium, and in the intermediate fraction of the endothelium. There was no peptidase found in the stroma. EDTA, cysteine, calf serum and calf aqueous inhibited this activity. The specificity and advantages of the substrate are discussed, and the clinical implications of a collagenase-like peptidase system within the cornea are noted.

PROTHROMBIN LEVELS DURING THE FIRST YEAR OF LIFE. OBSERVATIONS FOLLOWED BY THE SYNTHETIC SUBSTRATE (TAME) ASSAY OF NORMAL FULL-TERM INFANTS.

The determination of the prothrombin time, particularly the prothrombin content of plasma, is a useful but often neglected liver function test in the adult. 1-4 It occurred to us that similar studies might be of value in infancy during the period of life when most liver function tests are of equivocal value. 5-7 Since preliminary studies were encouraging, it became important to determine values for prothrombin and the prothrombin complex in the normal full-term infant. These values are the subject of this report. Materials and Methods A total of 28 normal full-term infants were followed during the first 12 to 18 months of life. The group included 22 Negro (12 male, ten female) and six white (two male, four female) infants. Each child was regularly examined by one of us (J. S.) in a well-baby clinic. The infants' weights were recorded on each visit. All initial determinations, with two exceptions,