Effect of muscle acyl phosphatase on the amino acid incorporation in cell-free systems

Abstract

Acyl phosphatase (E.C. 3.6.1.7) is an hydrolase which acts specifically on the splitting of the carboxyl-phosphate bond (1). In our laboratory this enzyme was purified from horse muscle (2) and some of its properties were stidued (3). The determination of the molecular weight and the isoelectic point indicate that muscle acyl phosphatase must be considered a small protein with basic properties; furthermore histochemical studies (4) have demonstrated thel ocalization of this enzyme in the soluble fraction of cytoplasm. Acyl phosphatase hydrolytic activity and its cytoplasmic localization may suggest the hypothesis of an interaction between this protein and systems of microsomal protein sythesis. It seemed therefore interesting to investigate the effect of horse muscle acyl phosphatase on the amino acid incorporaiton in vitro in microsomal cell-free systems. Our experiments have shown an inhibitory action of the eznyme. This protein could interface in protein synthesis either by means of its enzymatic properties, i.e. hydrolyzing the carboxyl-phosphate bonds of compounds correlated to this process, or by means of its basic nature. It is well known, in fact, from several works (5,6,7,8,9,10,11), that histones, protamines and generally polycations can play an inhibitory role on nuclear protein synthesis and gene expression, acting at various levels. In the present paper we report some studies aobut the inhibitory action of this enzyme on the ammino acid incorporation in cel-free systems from rat muscle and liver.