Jones R E, Plymate S R
Department of Medicine, Madigan Army Medical Center, Tacoma, Washington.
J Androl. 1993 Nov-Dec;14(6):428-32.
The synthesis of docosahexaenoyl coenzyme A (22:6-CoA) was studied in a long-chain fatty acid: CoASH ligase (AMP)-enriched fraction from human spermatozoa and was compared to palmitoyl CoA (16:0-CoA) synthesis. The pH optimum for 22:6 activation was 8.4, which was identical to the value obtained with 16:0. The Km for ATP was 0.5 mM when 22:6 was the acyl substrate; however, when 16:0 was incubated with the ligase preparation, the Km for ATP was 2.9 mM. When CoASH was varied and 22:6 was the fatty acyl acceptor, a pattern of negative cooperatively was observed. This was confirmed by a downwardly concave double-reciprocal plot, a Hill coefficient of 0.63, and an Rs in excess of 150. The Hill coefficient with 16:0 and CoASH was 0.94. Palmitic acid was demonstrated to be a competitive inhibitor of 22:6-CoA synthesis. Based upon these data, we conclude that the kinetics of spermatozoan ligase are complex, and, in addition, these data support the hypothesis that 22:6 may regulate ligase activity, and therefore free fatty acid utilization, in sperm.
辅酶A连接酶（AMP）的组分中研究了二十二碳六烯酰辅酶A（22:6-CoA）的合成，并将其与棕榈酰辅酶A（16:0-CoA）的合成进行比较。22:6激活的最适pH值为8.4，这与16:0得到的值相同。当22:6作为酰基底物时，ATP的Km为0.5 mM；然而，当16:0与连接酶制剂一起孵育时，ATP的Km为2.9 mM。当改变辅酶A（CoASH）浓度且22:6作为脂肪酰基受体时，观察到负协同效应模式。这通过向下凹的双倒数图、0.63的希尔系数和超过150的Rs得到证实。16:0与CoASH的希尔系数为0.94。已证明棕榈酸是22:6-CoA合成的竞争性抑制剂。基于这些数据，我们得出结论，精子连接酶的动力学很复杂，此外，这些数据支持22:6可能调节精子中连接酶活性，进而调节游离脂肪酸利用的假说。
