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.

Occurrence of prochymosin variants in the abomasum of bovine foetuses and calves.

Prochymosin variants were analysed in single abomasa from 67 foetuses (3-9 months of gestation) and 33 calves (about 6 weeks old) of Black-and-White cattle collected in a slaughter house. The method of agarose gel electrophoresis followed by detection of proteolytic activity was used. Three distinct prochymosins A, B and C that occurred singly or in pairs (with equal proteolytic activities of both components) were found. Chymosin A, B and C obtained after conversion of corresponding prochymosins, demonstrated similar electrophoretical mobilities like the three chymosin fractions contained in commercial rennin (Sigma, USA). Our chymosin B showed identical mobility as the amidated form of recombined chymosin B contained in Chymogen (Chr. Hansen's Lab., Denmark A/S). Prochymosin A, B and C in the examined animals were precursors of corresponding chymosins and were controlled by three separate codominant alleles. The following prochymosin phenotypes were found: AA (30), AB (32), AC (4), BB (29), BC (4) and CC (1). Chi-square analysis demonstrated significant differences between the observed and expected numbers of phenotypes. The gene frequencies of prochymosin A, B and C were 0.48, 0.47 and 0.05, respectively.

Prochymosin and pepsinogen potential activity and electrophoretic study of proteolytic fractions in the gastric and duodenal mucosal extracts from the first four day old lambs.

Potential proteolytic activity of prochymosin (PCh) and pepsinogen (PG) as well as relative activity of the proteolytic fractions in the mucosal extracts of the whole stomach, pyloric region of the stomach and duodenum were investigated. The main activity in the lambs stomach after birth demonstrated PCh however a small amount of PGA activity was also present. The highest activity of PCh from the whole stomach was observed in day 2 and 3, PG activity from the whole and pyloric region of the stomach increased in the first day of life and later was not significant by changed. Mucosal extracts of the whole stomach contained 3 to 4 of pepsinogen fractions of the fast migration (Pg1, Pg2, Pg3 and Pg4) in which Pg3 was of the highest activity in the majority of lambs. Pyloric region revealed 3 fractions: Pg2, of a small and Pg3 and Pg4 of high and equal activity. In duodenum Pg3 and Pg4 were of equal activity. The beginning of Pg2, Pg3 and Pg4 relative activity changes were observed in lambs stomach in respect to increase of Pg2 and decrease of Pg3 activity. The group of 3-4 fractions of slow electrophoretic migration contained probably progastricsin of small--and prochymosin of the highest activity within this group and a small non-pepsinogen fraction.