Abstract
1. 1. ATP:guanidinoacetate phosphotransferase (EC 2.7.3.1) has been purified by (NH 4) 2SO 4 fractionation, molecular sieving on Sephadex G-100 and DEAE-Sephadex chromatography. The enzyme, which has been purified 30-fold, appears to be homogeneous on analytical centrifugation, ion-exchange chromatography and gel electrophoresis. 2. 2. The molecular weight value obtained by analytical centrifugation (89 000 ± 2200) is near that calculated from amino acid composition (87 500). 3. 3. Glycocyamine and creatine kinases have very similar amino acid compositions. In the former enzyme, there is more tyrosine, glycine, alanine than in the latter and twice less the number of histidine residues. It contains 20 to 22 −SH groups per molecule and no cystine. 4. 4.|On fingerprint analysis of the tryptic hydrolysate of S-[1- 14 C]succinylglycocyamine kinase about half the number of peptides which would be expected from the 95 arginine + lysine residues are revealed. This fact suggests that the Nephthys coeca muscle glycocyamine kinase is composed of 2 similar subunits. Two neutral labelled peptides are found; one of them, containing much label, may correspond to the cysteine active site.
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