SummaryThe distribution and activity of alkaline phosphatase (E.C. 3.1.3.1), acid phosphatase (E.C. 3.1.3.2), catalase (E.C. 1.11.1.6), xanthine oxidase (E.C. 1.2.3.2), aldolase (E.C. 4.1.2.7 and 4.1.2.13), ribonuclease (E.C. 2.7.7.16) and carbonic anhydrase (E.C. 4.2.1.1) were studied in the major components of bovine milk. Fractionation was accomplished by centrifugation of milk, skim-milk and buttermilk, and ammonium sulphate precipitation of skim-milk serum. The range of activities found for the enzymes studied are tabulated together with the activities of some of the enzymes in mastitic milk, and the significance of the results obtained is discussed. No carbonic anhydrase activity was detected in any of the samples tested. The other enzymes studied were found to have a greater proportion of their total activity located in the skim-milk fraction. However, all of these enzymes except ribonuclease had a higher specific activity in the fat fraction.

SummarySuccinate dehydrogenase (SDH), lactate dehydrogenase (LDH), glutamateoxaloacetate transaminase (GOT), and acid and alkaline phosphatase are present in ram, bull, dog, rabbit, and human semen but the concentrations differ from one species to another. Amylase is found in the semen of all these species except the ram, and glucose·6-phosphate dehydrogenase (GDH) in all except the bull.Studies of the ram and bull showed that if a particular enzyme is present in whole semen, it occurs in both the spermatozoa and seminal plasma but there was often a great difference in the activity of the two fractions, e.g.· SDH and LDH activity was greater in the spermatozoa than in the plasma. SDH appears to be very tightly bound in ram spermatozoa since, unlike LDH, it is not released by sonic disruption. LDH, GOT, GDH, and acid phosphatase are leached out of ram and bull spermatozoa by sudden cooling (cold shock) or deep freezing.The enzyme content of ram testicular fluid is low compared with epididymal and vesicular fluids and some of the enzymes found in the seminal plasma probably have their origin in the epididymis and seminal vesicles.