Pathways of fatty acid synthesis and reducing equivalent generation in mammary gland of rat, sow, and cow

Adaptive Changes in Satellite Systems Related to Lipogenesis in Rat and Sheep Mammary Gland and in Adipose Tissue

“…The role of isocitrate dehydrogenase as a hydrogen generator has already been discussed and, on this point, the present scheme is in complete agreement with that proposed by Bauman et al [6]. Glutamate dehydrogenase may act in two capacities, as a deaminating enzyme in conjuction with transaminase reactions or as a transhydrogenase [32].…”

“…from 2-oxoglutarate to citrate. c) On the basis of isotopic evidence on bovine mammary gland, there is a one-for-one relationship between acetate oxidation and incorporation into lipid [6] and similar ratios have been observed in sheep (Table 4). The scheme in Fig.…”

“…The scheme of Bauman et at. [6] does, however, implicate the glutamate-oxaloacetate transaminase system, but this may be more related to bovine mammary tissue since we have found that neither glutamate-oxaloacetate transaminase nor glutamate-pyruvate transaminase were outstandingly high relative to the fatty acid synthetase activity in the sheep. The involvement of glutamate-oxaloacetate transaminase would also require the conversion of the oxaloacetate produced to malate before transporting it to the mitochondria, raising the problem of a source of this NADH in the cytosol for the interconversion when acetate is the sole substrate present.…”

“…The present scheme is an extension and modification of that proposed by Bauman et al [6]. The differences reside mainly in the recycling of a 2-0x0-glutarate to citrate by the reverse reactions of the tricarboxylic acid cycle and in the role ascribed to glutamate dehydrogenase.…”

“…Although an extensive, but somewhat selective, literature already exists on the changes of enzyme levels in response to lactation [1][2][3][4][5][6]7], it seemed important in the present context to obtain values a t specific points in the lactation cycle as this would permit the identification of constant and specific proportion groups of enzymes [8, 91. Some enzymes have, therefore been, reinvestigated and, in addition, many others have been added.…”