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The Stearoyl-CoA Desaturase(SCD) is a key enzyme, which converting palmitic acid(16:0) and stearic acid(18:0) to palmitoleic acid(16:1) and oleic acid(18:1), respectively. The concentration of oleic acid(18:1) in meat of beef cattle could influence both palatability and perception of meat. This experiment has conducted to determine relationship between the compositions of monounsaturated fatty acids and the SCD mRNA level in bovine liver and loin muscle tissue. The compositions of palmitoleic acid(16:1) and oleic acid(18:1) in loin muscle were 5% and 45% of total lipid and in liver were 2% and 20% of total lipid, respectively. On the other hand, the compositions of palmitic acid(16:0) and stearic acid(18:0) in loin muscle were 25% and 45% of total lipid and in liver were 14% and 43% of total lipid, respectively. The ratio of monounsaturated to saturated fatty acids(the desaturation index) was used as a measure of SCD activity in tissues. The average desaturation index in loin muscle was higher about 3.6-fold than that in liver. The desaturation index of oleate/stearate and palmitoleate/palmitate in loin muscle were higher 8-fold and 1.8-fold than those in liver, respectively, showing that the substrate specificity of SCD enzyme was very different between liver and muscle tissues. To determine whether the composition of monousaturated fatty acids in liver and muscle are dependent on SCD expression, SCD mRNA level was examined by RT-PRC analysis. The SCD mRNA level in loin muscle was higher about 3-fold than that in liver. Thus, the quantitative relationship between the desaturation index of fatty acid SCD mRNA was observed in liver and muscle. The difference in the compositions of monounsaturated fatty acids between bovine liver and muscle tissues may by due to different level of Stearoyl-CoA Desaturase mRNA.
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