The A9-Desaturase Enzyme System

Our understanding of the regulation of A9-desaturase in ruminants is limited, with current knowledge coming mainly from investigations on 

The relationship between substrate and product for A9-desaturase is reflected by the desaturase index, defined as [RA -t- (RA + VA)] (Kelsey et al., 2003). The desaturase index in milk fat represents a proxy for A9-desaturase and a several-fold range is observed among individuals. This is discussed in Section 3.5.2, but provides a strong indication that there are genetic differences among individuals with respect to this enzyme. 

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Figure 3.3. The A9-desaturase enzyme system showing the conversion of vaccenic acid (trans-11 18 1) to rumenic acid (cis-9, trans-11 CLA).

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