Biohydrogenation of linoleic and linolenic acids

The initial step in rumen biohydrogenation of linoleic and linolenic acids involves an isomerization of the cis-12 double bond to a trans-11... 

Figure 3.2. Pathways for ruminal and endogenous synthesis of rumenic acid (cis-9, trans-11 CLA) in the lactating dairy cow. Pathways for biohydrogenation of linoleic and linolenic acids yielding vaccenic acid trans-11 18 1) are shown in the rumen box and endogenous synthesis by A9-desaturase is shown in the mammary gland box. Adapted from Bauman et at. (2003).

In contrast to cis-9, trans-11 and trans-1, cis-9, the other isomers of CLA found in milk and body fat of ruminants appear to originate exclusively from rumen output. These are detected in rumen fluid (61) and duodenal fluid (39), and estimates of duodenal flow indicate that rumen output of these minor cis/trans, cis-cis, and trans-trans CLA isomers is greater than the trace amounts secreted in milk fat (39). The common theme to endogenously synthesized CLA isomers is A -desaturase and the cis-9 double bond that is added to trans-1 and trans- 1 monoenes. In contrast, there has been no demonstration that other mammalian desaturases act in a manner analogous to A -desaturase to synthesize CLA endogenously from mono-unsaturated fatty acids. Thus, these other CLA isomers found in trace levels in ruminant fat are of rumen origin and must represent intermediates in the ruminal biohydrogenation of linoleic and linolenic acids. 

---

See also in sourсe #XX -- [ , ]

---