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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Cleavage of the peptide bond of beta-alanyl-L-histidine (carnosine) induced by a Co~(III)-amine complexes:reaction,structure and mechanism
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Cleavage of the peptide bond of beta-alanyl-L-histidine (carnosine) induced by a Co~(III)-amine complexes:reaction,structure and mechanism

机译：Co〜（III）-胺配合物诱导的β-丙氨酰-L-组氨酸（肌氨酸）肽键的裂解：反应，结构和机理

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Cleavage of the peptide bond occurs when beta-alanyl-L-histidine (carnosine) reacts with [Co(tren)Cl_2]~+ (tren=tris(2-aminoethyl)amine) to give [Co(tren)(histidine)]~(2+) 1 and [Co(tren)(beta-alanine)]~(2+) 2.[Co(tren)(histidine)]~(2+) 1 crystallizes in the enantiomorphic space group P2_12_12_1 and 2 crystallizes in the P2_1/c space group.The mechanism of the cleavage reactions were studied in detail for the precursor [Co(tren)Cl_2]~+ and [Co(trien)Cl_2]~+,which convert into [Co(tren)(OH)_2]~+/[Co(tren)(OH)(OH_2)]~(2+) and [Co(trien)(OH)_2]~+/[Co(trien)(OH)(OH_2)]~(2+) in water at basic pH (trien=1,4,7,10-tetraazadecane).At a slightly basic pH,the initial coordination of the substrate (P-alanyl-L-histidine) is by the carboxylate group for the reaction with [Co(tren)Cl_2]~+.This is followed by a rate-limiting nucleophilic attack of the hydroxide group at the beta-alanyl-L-histidine carbonyl group.In a strongly basic reaction medium substrate,binding of the metal was through carboxylate and amine terminals.On the other hand,for the reaction between [cis-beta-Co(trien)Cl_2]~+ and beta-alanyl-L-histidine,the initial coordination of the substrate takes place via an imidazole ring nitrogen,independently,and followed by a nucleophilic attack of the hydroxide group at the beta-alanyl-L-histidine carbonyl group.The circular dichroism spectrum for 1 suggests that a very small extent of racemization of the amino acid (L-histidine) takes place during the cleavage reaction between [Co(tren)Cl_2]~+ and beta-alanyl-L-histidine.Reaction between [cis-beta-Co(trien)Cl_2]~+ and beta-alanyl-L-histidine also causes cleavage of the peptide bond,producing a free beta-alanyl molecule and a cationic fragment [cis-alpha-Co(trien)(histidine)]~(2+) 3 that crystallizes in the optically active space group P2_12_12_1.Unlike the previous case an appreciable degree of racemization of the L-histidine takes place during the reaction between [cis-beta-Co(trien)Cl_2]~+ and beta-alanyl-L-histidine.Crystals containing L-histidine and D-histidine fragments in the [cis-alpha-Co(trien)(histidine)]~(2+) moiety were crystallographically documented by mounting a number of randomly selected crystals.
机译：当β-丙氨酰基-L-组氨酸（肌氨酸）与[Co（tren）Cl_2]〜+（tren = tris（2-氨乙基）胺）反应生成[Co（tren）（组氨酸）]时，发生肽键断裂〜（2+）1和[Co（tren）（β-丙氨酸）]〜（2+）2。[Co（tren）（组氨酸）]〜（2+）1在对映空间群P2_12_12_1中结晶，而2在结晶中。研究了前体[Co（tren）Cl_2]〜+和[Co（trien）Cl_2]〜+转化为[Co（tren）（ OH）_2]〜+ / [Co（tren）（OH）（OH_2）]〜（2+）和[Co（trien）（OH）_2]〜// [Co（trien）（OH）（OH_2）]在碱性pH值下（trien = 1,4,7,10-四氮杂e）在水中〜（2+）。在弱碱性pH值下，底物（P-丙氨酰-L-组氨酸）的初始配位是由羧酸根与[Co（tren）Cl_2]〜+的反应。然后在β-丙氨酰-L-组氨酸羰基上发生氢氧基的限速亲核攻击。在强碱性反应介质中，金属是通过羧酸盐另一方面，对于[顺式-β-Co（trien）Cl_2]〜+与β-丙氨酰基-L-组氨酸的反应，底物的初始配位反应是通过咪唑环氮独立发生的。 1的圆二色性谱表明，氨基酸（L-组氨酸）的消旋程度很小。 [Co（tren）Cl_2]〜+与β-丙氨酰-L-组氨酸之间的裂解反应。[cis-beta-Co（trien）Cl_2]〜+与β-丙氨酰-L-组氨酸之间的反应也引起该肽的裂解键，产生一个游离的β-丙氨酰分子和一个阳离子片段[顺式-α-Co（trien）（组氨酸）]〜（2+）3，该片段在旋光性空间基团P2_12_12_1中结晶。在[顺式-β-Co（trien）Cl_2]〜+与β-丙氨酰-L-组氨酸的反应中，L-组氨酸发生消旋化。通过装入许多随机选择的晶体，从晶体学上记录了在[顺式-α-Co（trien）（组氨酸）]〜（2+）部分中包含L-组氨酸和D-组氨酸片段的金属。

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