Metabolism of leucine by the isolated perfused goat udder.
Seven lactating goat mammary glands from 6 goats were perfused for several hours in the presence of [U-14C]L-leucine (4 experiments) or [2-3H; 1-14C]DL-leucine (3 experiments) and received adequate quantities of glucose, acetate and amino acids. Radioactivity in casein was mainly recovered in leucine and 90% of casein leucine was derived from free plasma leucine. About 64% of the leucine molecules were used for casein synthesis. Up to 12% of the molecules were channelled into lipid synthesis, while the remaining (up to 24%) were metabolized to CO2. From the 3H/14C ratio of casein and casein leucine, it was calculated that 70-80% of the leucine molecules were reversibly transaminated before their incorporation into milk protein. However, only 4-8% of the plasma leucine molecules were transaminated during passage through the udder. Different pools for oxidation and for protein synthesis may be present in the goat mammary gland.
D000596:Amino Acids / Q000096:biosynthesis; D000818:Animals; D002364:Caseins / Q000096:biosynthesis; D005227:Fatty Acids / Q000096:biosynthesis; D005260:Female; D006041:Goats / Q000378:metabolism*; D007774:Lactation; D007930:Leucine / Q000378:metabolism*; D008321:Mammary Glands, Animal / Q000378:metabolism*; D008892:Milk / Q000378:metabolism; D010477:Perfusion; D011247:Pregnancy; D013237:Stereoisomerism
D000596:Amino Acids; D002364:Caseins; D005227:Fatty Acids; D007930:Leucine