Activation of a pro-enzyme by a stoichiometric reaction with another protein. The reaction between prothrombin and staphylocoagulase

Microtube coagulase test for detection of coagulase-positive staphylococci

Studies were performed to determine the sensitivity and specificity of a new microtube method for the detection of coagulase production by Staphylococcus aureus. Rabbit plasma containing EDTA was added to and lyophilized in API microtubes. Two standard coagulase plasmas containing EDTA were used in the conventional macrotube test and served as a basis for comparison. No false-positive or false-negative reactions were encountered with the microtube system. With this system, 53% of the coagulase-positive strains tested were detected within 1 h after inoculation, 82% were detected after 2 h, 97% were detected after 3 h, and 99% were detected after 4 h. With the first conventional method, 45, 81, 96, and 98% of the positive strains were detected in 1, 2, 3, and 4 h, respectively, whereas with the second conventional method, only 6% of the positive strains were detected in 1 h, 24% in 2 h, 66% in 3 h, and 81% in 4 h. With the microtube method, 5 of the 139 coagulase-producing strains studied reverted to negative between 5 and 24 h after inoculation, whereas 9 reverted with the more rapid conventional method, and no reversions occurred with the second conventional method. All reversions involved strains which caused gelation of plasma within 1 h after inoculation. The data obtained showed that 99% of the coagulase-positive strains tested could be detected within 4 h by the microtube method. In addition, the microtube method offers a more convenient and economical format for the performance of the coagulase tube test.

Rapid and direct staphylocoagulase assay that uses a chromogenic substrate for identification of Staphylococcus aureus

A rapid and direct assay of staphylocoagulase that uses chromogenic substrate Chromozym TH was developed for the routine identification of Staphylococcus aureus. False-positive and false-negative reactions were eliminated by measuring the activity of staphylocoagulase-prothrombin complex directly. The method was compared with three clotting assays. The results show that the new assay is specific, quantitative, and easily automated. If offers clinical laboratories a more reliable assay of staphylocoagulase and is a valuable aid for the rapid identification of S. aureus.

Reversible activation of proactivator (factor B) of the alternative pathway without cleavage of the molecule

The serum of a patient (M.C.) with chronic glomerulonephritis and renal deposits of IgA, C3, and properdin converted C3 on overnight exposure of 0 degrees C. The cold reaction was dependent on immunoglobulin, initiating factor, Factors B and D, and magnesium but not on properdin. Factor B, the C3-cleaving enzyme in this reaction, was used in zymogen form. After participation in this rection, Factor B zymogen in M.C. serum could be fully activated by cobra venom factor (CVF) at 37 degrees C. That activation without fragmentation was not due to an abnormal form of Factor B was shown by its typical cleavage on incubation of MC. serum with CVF or C3b or after depletion of C3b inactivator. The evidence indicates that in the cold reaction only the initial C3 convertase of the alternative parhway is formed and that this enzyme is responsible for the observed C3 consumption.

Purification and properties of staphylocoagulase

Staphylocoagulase, an exoprotein of coagulase-positive Staphylococci, has been purified to a state in which only trace amounts of contaminating proteins are detectable. Aspartic acid was found as a single N-terminal amino acid in this preparation. The molecular weight is 61 000; the isoelectric point lies as pH 4.53. The amino acid composition was determined.

The influence of cadmium ions on the adsorption of prothrombin onto A1(OH)3 as a means to purify prothrombin

1. In the presence of CdSO4(1mM),Al(OH)3(1.3% w/v) completely adsorbs the coagulation factors VII, IX, and X from normal plasma, but factor II (prothrombin) is adsorbed for about 50% only.2. A purification procedure for factor II is developed, using Al(OH)3 adsorption in the presence of Cd2+ as a first step and using column chromatography only once. A 750-fold purification is obtained at a 24% yield. 3. Comparison of the prothrombin thus obtained, with prothrombin isolated by the method of Kisiel and Hanahan (Biochim. Biophys. Acta (1973) 304, 103-113) does not show significant differences in amino acid composition, N-terminal amino acid, molecular weight or immunological properties. 4. Comparison of the two prothrombin preparations in a thrombin-generating system shows that although the final yield of thrombin from a given amount of prothrombin in both preparations is the same, the initial velocity of thrombin formation from our preparation is comparable to that of native prothrombin, whereas the other preparation is converted significantly slower.