Nagai M, Watanabe M, Endoh M, Danbara H
Department of Microbiology, School of Pharmaceutical Sciences, Kitasato University, Tokyo, Japan.
Biol Pharm Bull. 1997 Feb;20(2):193-5. doi: 10.1248/bpb.20.193.
The ability of Bordetella heat-labile toxin (HLT) to induce ischemic lesions after intracutaneous injection to guinea pig skin was lost following incubation at 37 degrees C with long-chain saturated acyl-CoA and acyl-carnitine compounds. Short-chain unsaturated acyl-CoA compounds, however, were less potent in inhibiting the induction of HLT activity. Long-chain saturated acyl-CoA and acyl-carnitine compounds, potently inhibited the induction of this activity. On incubation with HLT at 0 degrees C, a long-chain saturated acyl-CoA compound, palmitoyl-CoA, did not inhibit HLT activity. When first mixed with bovine serum albumin or dimethyl-beta-cyclodextrin, palmitoyl-CoA lost the ability to inhibit HLT activity. Binding of 14C-palmitoyl-CoA to HLT was measured by Scatchard analysis. The Bmax values of HLT (2.75 mol/mol of protein) were higher than that of acyl-CoA-binding protein from bovine liver (0.95 mol/mol of protein). Neither acyl-CoA hydrolase nor acyl-CoA ligase was detected in the HLT preparation. These results suggest that the acyl-CoA and acyl-carnitine compounds bind directly to HLT and produce a critical change in conformation required for HLT activity.
将博德特氏菌热不稳定毒素（HLT）皮内注射到豚鼠皮肤后诱导缺血性损伤的能力，在37℃下与长链饱和酰基辅酶A和酰基肉碱化合物孵育后丧失。然而，短链不饱和酰基辅酶A化合物在抑制HLT活性诱导方面的效力较低。长链饱和酰基辅酶A和酰基肉碱化合物能有效抑制这种活性的诱导。在0℃下与HLT孵育时，一种长链饱和酰基辅酶A化合物棕榈酰辅酶A不会抑制HLT活性。当首先与牛血清白蛋白或二甲基-β-环糊精混合时，棕榈酰辅酶A失去了抑制HLT活性的能力。通过Scatchard分析测定了14C-棕榈酰辅酶A与HLT的结合。HLT的Bmax值（2.75摩尔/摩尔蛋白质）高于牛肝酰基辅酶A结合蛋白的Bmax值（0.95摩尔/摩尔蛋白质）。在HLT制剂中未检测到酰基辅酶A水解酶或酰基辅酶A连接酶。这些结果表明，酰基辅酶A和酰基肉碱化合物直接与HLT结合，并对HLT活性所需的构象产生关键变化。
