Shimshoni Jakob A, Basselin Mireille, Li Lei O, Coleman Rosalind A, Rapoport Stanley I, Modi Hiren R
National Institute on Aging, National Institutes of Health, Bethesda, MD, USA.
Biochim Biophys Acta. 2011 Mar;1811(3):163-9. doi: 10.1016/j.bbalip.2010.12.006. Epub 2010 Dec 22.
The ability of chronic valproate (VPA) to reduce arachidonic acid (AA) turnover in brain phospholipids of unanesthetized rats has been ascribed to its inhibition of acyl-CoA synthetase (Acsl)-mediated activation of AA to AA-CoA. Our aim was to identify a rat Acsl isoenzyme that could be inhibited by VPA in vitro.
Rat Acsl3-, Acsl6v1- and Acsl6v2-, and Acsl4-flag proteins were expressed in E. coli, and the ability of VPA to inhibit their activation of long-chain fatty acids to acyl-CoA was estimated using Michaelis-Menten kinetics.
VPA uncompetitively inhibited Acsl4-mediated conversion of AA and of docosahexaenoic (DHA) but not of palmitic acid to acyl-CoA, but did not affect AA conversion by Acsl3, Acsl6v1 or Acsl6v2. Acsl4-mediated conversion of AA to AA-CoA showed substrate inhibition and had a 10-times higher catalytic efficiency than did conversion of DHA to DHA-CoA. Butyrate, octanoate, or lithium did not inhibit AA activation by Acsl4.
VPA's ability to inhibit Acsl4 activation of AA and of DHA to their respective acyl-CoAs, when related to the higher catalytic efficiency of AA than DHA conversion, may account for VPA's selective reduction of AA turnover in rat brain phospholipids, and contribute to VPA's efficacy against bipolar disorder.
慢性丙戊酸（VPA）降低未麻醉大鼠脑磷脂中花生四烯酸（AA）周转的能力，被归因于其对酰基辅酶A合成酶（Acsl）介导的AA活化为AA - CoA的抑制作用。我们的目的是鉴定一种在体外可被VPA抑制的大鼠Acsl同工酶。
大鼠Acsl3、Acsl6v1、Acsl6v2和Acsl4 - flag蛋白在大肠杆菌中表达，使用米氏动力学评估VPA抑制它们将长链脂肪酸活化为酰基辅酶A的能力。
VPA非竞争性抑制Acsl4介导的AA和二十二碳六烯酸（DHA）而非棕榈酸向酰基辅酶A的转化，但不影响Acsl3、Acsl6v1或Acsl6v2对AA的转化。Acsl4介导的AA向AA - CoA的转化表现出底物抑制，且催化效率比DHA向DHA - CoA的转化高10倍。丁酸盐、辛酸盐或锂不抑制Acsl4对AA的活化。
VPA抑制Acsl4将AA和DHA活化为各自酰基辅酶A的能力，与AA转化比DHA转化具有更高的催化效率相关，这可能解释了VPA对大鼠脑磷脂中AA周转的选择性降低，并有助于VPA治疗双相情感障碍的疗效。
