Adenylate Kinase of Porcine Heart

Abstract

The activity of adenylate kinase (ATP : AMP‐phosphotransferase, EC 2.7.4.3) in porcine heart is about one‐sixth that in porcine skeletal muscle on a wet weight basis. Essentially all of the activity of the heart preparations, 70–80 units/g tissue, was present in the soluble fraction. On the basis of acid stability at pH 3.5 and O °C and behavior on isoelectrofocusing, there appear to be at least two adenylate kinases in heart, one acid‐labile type having an isoelectric point between 4.7–7.5 and the other an acid‐stable type having an isoelectric point at 9.3. The acid‐stable adenylate kinase was purified approximately 1300‐fold from heart homogenate. The purified enzyme had a molecular weight of 21500 and migrated in gel electrophoresis as a single band. A mixture prepared together with purified muscle enzyme also gave a single narrow band in gel electrophoresis. Amino acid composition was found to be Asx13, Thr14, Ser11, Glx25, Pro6, Gly19, Ala8, Val17, Met6, Ile9, Leu18, Tyr7, Phe5, His2, Lys21, Arg11, Cys2 (as cysteine) and no tryptophan. Fingerprinting showed correspondence of all major spots of the tryptic peptides from heart and skeletal muscle enzymes preparations. The total amino acid sequence of the skeletal muscle enzyme is accounted for by the peptides found on fingerprinting. These results strongly suggest that the major acid‐stable adenylate kinase from porcine heart is identical to porcine skeletal muscle adenylate kinase. Copyright © 1974, Wiley Blackwell. All rights reserved