Prochymosin polymorphism in calves of black-and-white cattle and their crosses with Simental bulls.
Polymorphism of prochymosin was observed in individual calf abomasa, using agarose gel electrophoresis followed by detection of proteolytic activity. Abomasum samples were randomly collected during slaughtering from 239 and 146 calves (3-5 weeks old) of Black-and-White cattle and their crosses with Simental bulls, respectively. Four distinct prochymosins were found and, according to their decreasing electrophoretic mobility in alkaline agarose gel, termed as prochymosin A, D, B and C which occurred singly and in pairs (then with equal proteolytic activities of both components). Prochymosin A, B and C (designation according to FOLTMANN, 1966) activated at pH 4.7 was transformed into electrophoretically distinct chymosin. When prochymosin D was activated at this pH, chymosin D showed similar mobility as chymosin B both at alkaline and acidic pHs. Prochymosin variants occurred at genetical equilibrium in nine and ten phenotypes in the first and second genetic group. The distribution of phenotypes in the two groups differed significantly (P < 0.05). The gene frequencies of prochymosin A, D, B and C were 0.35, 0.11, 0.52 and 0.02 in Black-and-White calves, and 0.39, 0.08, 0.47 and 0.06 in crosses, respectively. These prochymosins were controlled by four pairs of codominant alleles. A possible correlation of the results obtained by FOLTMANN (1966) with ours and those of ASATO and RAND (1972, 1977) was discussed.
D000018:Abomasum / Q000201:enzymology; D000818:Animals; D002417:Cattle / Q000235:genetics*; D012085:Chymosin / Q000235:genetics*; D003433:Crosses, Genetic; D004587:Electrophoresis, Agar Gel / Q000662:veterinary; D004792:Enzyme Precursors / Q000235:genetics*; D005260:Female; D008297:Male; D010641:Phenotype; D011110:Polymorphism, Genetic
D004792:Enzyme Precursors; C032443:prorennin; D012085:Chymosin