Uridine phosphorylase from Escherichia coli B. Enzymatic and molecular properties.

Uridine phosphorylase (EC 2.4.2.3) from Escherichia coli B is an oligomeric protein composed of four identical subunits of 29,000 mol. wt. The enzyme has four half-cystine residues per subunit titrable only in denaturing condition. No disulphide linkages either inter- or intra-chain are present. The isoelectric point is 5.25. The enzyme shows strict specificity toward uridine and 5-methyluridine and is inhibited by thymine, deoxycytidine and heavy metal ions.