Resolution of 5′-mononucleotidase and non-specific phosphatase activities from skeletal muscles

Abstract

The 5’-nucleotidases (5’-ribonucleoside phosphohydrolase, EC 3.1.3.5) are widely distributed in animal and plant tissues and in microorganisms [l-lo] . The occurrence of the enzyme activity in heart muscle was originally reported by Reis [ 1 ] and recently confirmed by Burger and Lowenstein [ 1 l] ; its presence in skeletal muscle, however, has never been clearly demonstrated. Thus in 1940 Reis [2] described an enzyme activity catalyzing the dephosphorylation of IM-S’-P in muscle extracts from various sources under conditions in which &glycerophosphate was hydrolyzed at a much slower rate. On the other hand Purzycka [ 121 and Kendrick-Jones and Perry [ 131 failed to detect appreciable dephosphorylation of AM-5’-P in rat skeletal muscle, at least under conditions in which the mononucleotide was acted upon by adenylic deaminase and myokinase. In view of the paramount importance of adenine nucleotides in the biochemical events of muscular contraction, we have reinvestigated the problem of the 5’-nucleotidase occurrence in muscle. The present study reports on enzymes that hydrolyze 5’-mononucleotides in skeletal muscles from different sources. Muscle 5’-nucleotidases can be readily separated from non-specific phosphatases by Sephadex G-1 00 gel filtration. Different ratios between 5’-nucleotidase and non-specific phosphatase are observed in muscle extracts from various animals. Furthermore the 5’nucleotidases differ in their specificity towards 5’mononucleotides according to their origin. 2. Materials and methods