Grove Theresa J, Sidell Bruce D
School of Marine Sciences, University of Maine, Orono, ME 04469, USA.
Comp Biochem Physiol B Biochem Mol Biol. 2004 Sep;139(1):53-63. doi: 10.1016/j.cbpc.2004.06.005.
Antarctic notothenioid fishes possess large lipid stores that are important fuels for aerobic metabolism. Oxidative muscle tissues of these animals oxidize long-chain mono-unsaturated fatty acids more readily than saturated fatty acids. The mechanistic basis(es) for the substrate specificity of their fatty acid-oxidizing pathway is unknown. We examined the substrate specificity of fatty acyl coenzyme A synthetase (FACS) to determine whether the enzyme contributes to targeting unsaturated fatty acids for preferential transport into mitochondria as fuels for beta-oxidation. Maximal activities of FACS were measured in isolated mitochondria from Notothenia coriiceps and Chaenocephalus aceratus oxidative skeletal muscles in the presence of fatty acids differing in chain lengths and degrees of unsaturation. With the exception of C(22:6), maximal activities were greater with unsaturated substrates than with C(16:0), a saturated fatty acid. Monoenoic fatty acids did not produce the highest activities. Predicted amino acid sequences of FACS from Antarctic C. aceratus, Gobionotothen gibberifrons, and N. coriiceps and sub-Antarctic Notothenia angustata and Eleginops maclovinus were determined to identify amino acid candidates that may be important for determining the substrate specificity of FACS. Substitutions cysteine548 and polar threonine552 within the putative fatty acid binding pocket may contribute to preference for unsaturated fatty acyl substrates compared to saturated fatty acids.
南极南极鱼科鱼类拥有大量脂质储备，这些脂质是有氧代谢的重要燃料。这些动物的氧化型肌肉组织氧化长链单不饱和脂肪酸比饱和脂肪酸更容易。其脂肪酸氧化途径底物特异性的机制基础尚不清楚。我们研究了脂肪酰辅酶A合成酶（FACS）的底物特异性，以确定该酶是否有助于将不饱和脂肪酸靶向优先转运到线粒体中作为β氧化的燃料。在存在链长和不饱和度不同的脂肪酸的情况下，测量了来自小头南极鱼和裸头冰鱼氧化型骨骼肌的分离线粒体中FACS的最大活性。除了C(22:6)外，不饱和底物的最大活性高于饱和脂肪酸C(16:0)。单烯脂肪酸并未产生最高活性。确定了来自南极裸头冰鱼、吉氏南极鱼、小头南极鱼以及亚南极窄头南极鱼和麦氏智利鲈的FACS的预测氨基酸序列，以鉴定可能对确定FACS底物特异性很重要的氨基酸候选物。与饱和脂肪酸相比，假定的脂肪酸结合口袋内的半胱氨酸548和极性苏氨酸552的取代可能有助于对不饱和脂肪酰底物的偏好。
