An amino acid sequence in the active centre of phosphoglucomutase

Abstract

The presence of phosphate in phosphogluco- mutase was first demonstrated by Jagannathan & Luck (1949), who also showed that it may readily be exchanged with phosphate in the substrates and that it is thus probably involved in the active centre of the enzyme. Anderson & Joll6s (1957) observed that it was not released from the protein even under strong acid conditions and were able to isolate serine phosphate from the partially hydrolysed enzyme. This offered the possibility of studying the amino acid sequence around the point of attachment of the phosphate by isotopic tech- niques. In a preliminary study of the peptides produced from a partial hydrolysate of phosphoglucomutase labelled with 38p, Koshland & Erwin (1957) and SerP. Gly. Glu. Ala. - Val. [For definitions of the abbreviations of amino acids used in this paper see Biochem. J. (1957), 68, 6.] This was very similar to that found in trypsin and-chymotrypsin around the serine residue that can react with diisopropyl phosphorofluoridate. The sequence Asp. Ser. Gly thus appeared to be a common feature of enzymes with rather dissimilar fimctions, and these conclusions have been discussed by several authors in connexion with the problem of the relationship between structure and function (Luxury, 1959;