Cole K R, Kumar S, Trong H L, Woodbury R G, Walsh K A, Neurath H
Department of Biochemistry, University of Washington, Seattle 98195.
Biochemistry. 1991 Jan 22;30(3):648-55. doi: 10.1021/bi00217a009.
The amino acid sequence of rat mast cell carboxypeptidase has been determined. The major form has 308 residues; a minor form has an additional (glutamyl) residue at the amino terminus that may indicate an alternate cleavage site during zymogen activation. The enzyme is homologous to pancreatic carboxypeptidases A and B, with conservation of the functional amino acid residues of the active site. The putative substrate binding site resembles that of carboxypeptidase A, although other structural features bear more similarity to carboxypeptidase B. Mast cell carboxypeptidase retains enzymatic activity toward a peptide substrate (angiotensin I) while bound within the granular matrix of the rat connective tissue mast cells. Evidence is presented to suggest that a cluster of positively charged lysyl and arginyl residues binds the enzyme to the negatively charged heparin of the granular matrix but leaves the active site exposed to bind and cleave peptide substrates.
已确定大鼠肥大细胞羧肽酶的氨基酸序列。主要形式有308个残基；一种次要形式在氨基末端有一个额外的（谷氨酰基）残基，这可能表明在酶原激活过程中有一个替代的切割位点。该酶与胰腺羧肽酶A和B同源，活性位点的功能性氨基酸残基保守。推测的底物结合位点类似于羧肽酶A，尽管其他结构特征与羧肽酶B更相似。肥大细胞羧肽酶在结合于大鼠结缔组织肥大细胞的颗粒基质内时，对肽底物（血管紧张素I）仍保留酶活性。有证据表明，一组带正电荷的赖氨酸和精氨酸残基将该酶与颗粒基质带负电荷的肝素结合，但使活性位点暴露以结合和切割肽底物。
