Metabolic adaptations during lactogenesis. Fatty acid and lactose synthesis in cow mammary tissue.
1. Mammary-tissue biopsies were obtained from multiparous cows at 30 and 7 days pre partum and 7 and 40 days post partum. Investigations of the effect of lactogenesis on fatty acid and lactose synthesis involved measurements of biosynthetic capacity (tissue-slice incubations in vitro) and activities of relevant enzymes. 2. Fatty acid synthesis from acetate increased over 20-fold from 30 days pre partum to 40 days post partum. Changes in the lipogenic capacity of mammary-tissue slices more closely paralleled increases in the activities of acetyl-CoA carboxylase (EC 6.4.1.2) and acetyl-CoA synthetase (EC 6.2.1.1) than of other enzymes involved in acetate incorporation into fatty acids or in NADPH generation. 3. Lactose biosynthesis by mammary-tissue slices, lactose synthetase activity (EC 2.4.1.22) and alpha-lactalbumin concentration were all negligible at 30 days pre partum but increased 2.5-4-fold between 7 days pre partum and 40 days post partum. Phosphoglucomutase (EC 2.7.5.1), UDP-glucose pyrophosphorylase (EC 2.7.7.9) and UDP-glucose 4-epimerase (EC 5.1.3.2) had substantial activities at 30 days pre partum and increased less dramatically during lactogenesis. 4. Results are consistent with acetyl-CoA carboxylase and perhaps acetyl-CoA synthetase representing the regulatory enzyme(s) in fatty acid synthesis, with lactose synthetase (alpha-lactalbumin) serving a similar function in lactose biosynthesis.
D000085:Acetates / Q000378:metabolism; D000105:Acetyl Coenzyme A; D000103:Acetyl-CoA Carboxylase / Q000378:metabolism; D000818:Animals; D001706:Biopsy; D002238:Carbohydrate Epimerases / Q000378:metabolism; D002245:Carbon Dioxide / Q000096:biosynthesis; D002250:Carbon Radioisotopes; D002417:Cattle; D003066:Coenzyme A Ligases / Q000378:metabolism; D046508:Culture Techniques; D005227:Fatty Acids / Q000096:biosynthesis*; D005260:Female; D005947:Glucose; D007768:Lactalbumin / Q000378:metabolism; D007774:Lactation; D007785:Lactose / Q000096:biosynthesis*; D007788:Lactose Synthase / Q000378:metabolism; D008321:Mammary Glands, Animal / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000378:metabolism; D010733:Phosphoglucomutase / Q000378:metabolism; D011247:Pregnancy; D013997:Time Factors; D014539:Uridine Diphosphate Sugars
D000085:Acetates; D002250:Carbon Radioisotopes; D005227:Fatty Acids; D014539:Uridine Diphosphate Sugars; D002245:Carbon Dioxide; D000105:Acetyl Coenzyme A; D007768:Lactalbumin; D007788:Lactose Synthase; D009713:Nucleotidyltransferases; D002238:Carbohydrate Epimerases; D010733:Phosphoglucomutase; D003066:Coenzyme A Ligases; D000103:Acetyl-CoA Carboxylase; D005947:Glucose; D007785:Lactose