| Summary: | The thermal stability and parameters of the Michaelis-Menten kinetics of engineered variant of recombinant reindeer chymosin (Rangifer tarandus) with a point amino acid substitution Lys53→Glu were studied. The values of the threshold of thermal inactivation of the studied enzyme and commercial recombinant cow chymosin coincided and amounted to 50 °C. The engineered reindeer enzyme showed the greatest affinity to the used chromogenic substrate, its Michaelis constant (Km) was 1,5–4,7 times lower than the same indicator of commercial recombinant chymosins. The catalytic rate constants (kcat) of the engineered variant of deer chymosin and recombinant camel chymosin were comparable. In terms of specificity (kcat/Km), the chymosins of reindeer and cow surpassed the genetically engineered analogue of the chymosin of the single-humped camel by 1,7 times.
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