CONDITIONS FOR SELF-CATALYSED INACTIVATION OF CARNITINE ACETYLTRANSFERASE - A NOVEL FORM OF ENZYME INHIBITION
CONDITIONS FOR SELF-CATALYSED INACTIVATION OF CARNITINE ACETYLTRANSFERASE - A NOVEL FORM OF ENZYME INHIBITION
复制标题
DOI：
10.1042/bj1110225
复制
发表时间：
1969-01-01
影响因子：
4.1
通讯作者：
TUBBS, PK
中科院分区：
文献类型：
--
作者：
CHASE, JFA;TUBBS, PK
1.在溴乙酰-（−）-肉毒碱加CoA或溴乙酰-CoA加（−）-肉毒碱存在下，肉毒碱乙酰转移酶被非常迅速地抑制。2.在适当的条件下，可用溴乙酰基底物类似物滴定酶;在每种情况下，需要约1 mol抑制剂才能完全溶解1 mol分子量为58000±3000的酶。3.溴乙酰辅酶A加（-）-肉毒碱的抑制作用导致形成一种无活性的酶，含有化学计量量的结合腺嘌呤核苷酸和（-）-肉毒碱，其形式不能通过凝胶过滤除去。这被证明是S-羧甲基-CoA（-）-肉毒碱酯。4.受抑制的酶在4°长时间静置后缓慢恢复活性。5.与S-羧甲基-CoA（−）-肉毒碱酯孵育可缓慢抑制肉毒碱乙酰转移酶。6.结合S-羧甲基-CoA（-）-肉毒碱酯的酶的形成进行了讨论。据推测，所产生的抑制反映了酯与酶上的CoA和肉毒碱结合位点的结合及其随后的非常缓慢的解离。这些观察结果证实，肉毒碱乙酰转移酶可以形成三元酶底物复合物，这似乎也是与肉毒碱棕榈酰转移酶和胆碱乙酰转移酶的情况。
1. Carnitine acetyltransferase is very rapidly inhibited in the presence of bromoacetyl-(−)-carnitine plus CoA or of bromoacetyl-CoA plus (−)-carnitine. 2. Under appropriate conditions, the enzyme may be titrated with either bromoacetyl substrate analogue; in each case about 1mole of inhibitor is required to inactivate completely 1mole of enzyme of molecular weight 58000±3000. 3. Inhibition by bromoacetyl-CoA plus (−)-carnitine results in the formation of an inactive enzyme species, containing stoicheiometric amounts of bound adenine nucleotide and (−)-carnitine in a form that is not removed by gel filtration. This is shown to beS-carboxymethyl-CoA (−)-carnitine ester. 4. The inhibited enzyme recovers activity slowly on prolonged standing at 4°. 5. Incubation withS-carboxymethyl-CoA (−)-carnitine ester causes a slow inhibition of carnitine acetyltransferase. 6. The formation of boundS-carboxymethyl-CoA (−)-carnitine ester by the enzyme is discussed. Presumably the resulting inhibition reflects binding of the ester to both the CoA- and carnitine-binding sites on the enzyme and its consequent very slow dissociation. These observations confirm that carnitine acetyltransferase can form ternary enzyme–substrate complexes; this also appears to be the case with carnitine palmitoyltransferase and choline acetyltransferase.