Catabolism of thymidine in human blood platelets purification and properties of thymidine phosphorylase

Biochimica et Biophysica Acta (BBA) - Nucleic Acids and Protein Synthesis Pub Date : 1981-07-27 DOI:10.1016/0005-2787(81)90174-X

C. Desgranges, G. Razaka, M. Rabaud, H. Bricaud

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引用次数: 99

Abstract

A pyrimidine nucleoside phosphorylase was partially purified from human blood platelets. The purified enzyme, as well as crude enzyme preparations, catalyses the phosphorolysis of thymidine and deoxyuridine, but not of uridine, and is able to catalyse direct pentosyl transfer from these deoxyribonucleosides to uracil or thymine; this enzyme has the properties of a thymidine phosphorylase. It has a molecular weight of about 110 000 and is composed of two identical subunits; it is phosphate dependent, has a maximal activity at a pH value of 5.7, and an isoelectric point of 4.4. This enzyme was mainly of cytoplasmic origin. Although platelet thymidine phosphorylase could promote the degradation or synthesis of thymidine, intact platelets degraded thymidine but were not able to synthesize thymidine from thymine. Blood platelets may play an important role in the degradation of plasma thymidine.

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胸腺嘧啶在人血小板中的分解代谢纯化及胸腺嘧啶磷酸化酶的性质

从人血小板中部分纯化出嘧啶核苷磷酸化酶。纯化酶和粗酶制剂催化胸腺嘧啶和脱氧尿嘧啶的磷酸化，但不能催化尿嘧啶的磷酸化，并且能够催化戊基从这些脱氧核糖核苷直接转移到尿嘧啶或胸腺嘧啶;这种酶具有胸腺嘧啶磷酸化酶的特性。它的分子量约为11万，由两个相同的亚基组成;它依赖于磷酸盐，在pH值为5.7时具有最大活性，等电点为4.4。这种酶主要来源于细胞质。虽然血小板胸腺嘧啶磷酸化酶可以促进胸腺嘧啶的降解或合成，但完整的血小板可以降解胸腺嘧啶，但不能从胸腺嘧啶合成胸腺嘧啶。血小板可能在血浆胸苷的降解中起重要作用。

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Biochimica et Biophysica Acta (BBA) - Nucleic Acids and Protein Synthesis

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