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Adenylate kinase (ATP:AMP phosphotransferase) has been purified 490‐fold from porcine muscle with a final yield of 60 mg/kg muscle. The amino‐acid composition is Asp11, Asn2, Thr14, Ser11, Glu19, Gln6, Pro6, Gly19, Ala8, Cys2, Val17, Met6, Ile9, Leu18. Tyr7, Phe5, Lys21, His2, Arg11. The protein molecule is a single polypeptide chain of 194 amino‐acid residues with an acetyl‐methionine at the N‐terminus and a lysine residue at the C‐terminus. Cyanogen bromide cleavage of carboxymethylated adenylate kinase yielded six fragments which were further degraded by using trypsin, chymotrypsin, thermolysin, subtilisin or α‐protease. Sequence data on the resulting peptides are summarized in the present report, full details are given in a supplementary paper which has been deposited at CNRS from where copies can be obtained. The primary structure of porcine adenylate kinase is: Ac‐Met‐Glu‐Glu‐Lys‐Leu‐Lys‐Lys‐Ser‐Lys‐Ile10‐Ile‐Phe‐Val‐Val‐Gly‐Gly‐Pro‐Gly ‐ Ser‐Gly20‐Lys‐Gly‐Thr‐Gln‐Cys‐Glu‐Lys‐Ile‐Val‐Gln30‐Lys‐Tyr‐Gly‐Tyr‐Thr‐His‐Leu‐Ser‐Thr‐Gly40‐Asp‐Leu‐Leu‐Arg‐Ala‐Glu‐Val‐Ser‐Ser‐Gly50‐Ser‐Ala‐Arg‐Gly‐Lys‐Met‐Leu‐Ser‐Glu‐Ile60‐Met‐Glu‐Lys‐Gly‐Gln‐Leu‐Val‐Pro‐Leu‐Glu70‐Thr‐Val‐Leu‐Asp‐Met‐Leu‐Arg‐Asp‐Ala‐Met80‐Val‐Ala‐Lys‐Val‐Asp‐Thr‐Ser‐Lys‐Gly‐Phe90‐Leu‐Ile‐Asp‐Gly‐Tyr‐Pro‐Arg‐Glu‐Val‐Lys100‐Gln‐Gly‐Glu‐Glu‐Phe‐Glu‐Arg‐Lys‐Ile‐Gly110‐Gln‐Pro‐Thr‐Leu‐Leu‐Leu‐Tyr‐Val‐Asp120‐Ala‐Gly‐Pro‐Glu‐Thr‐Met‐Thr‐Lys‐Arg‐Leu‐Leu130‐Lys‐Arg‐Gly‐Glu‐Thr‐Ser‐Gly‐Arg‐Val‐Asp140‐Asp‐Asn‐Glu‐Glu‐Thr‐Ile‐Lys‐Lys‐Arg‐Leu150‐Glu‐Thr‐Tyr‐Tyr‐Lys‐Ala‐Thr‐Glu‐Pro‐Val160‐Ile‐Ala‐Phe‐Tyr‐Glu‐Lys‐Arg‐Gly‐Ile‐Val170‐Arg‐Lys‐Val‐Asn‐Ala‐Glu‐Gly‐Ser‐Val‐Asp180‐Asp‐Val‐Phe‐Ser‐Gln‐Val‐Cys‐Thr‐His‐Leu190‐Asp‐Thr‐Leu‐Lys.

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GTP‐AMP phosphotransferase has been purified 116‐fold with a yield of 24% from beef heart mitochondria using freeze‐thawing, alkali and acid treatment and successive column chromatography on phosphocellulose, Sephadex G‐100 and blue‐dextran–Sepharose. It has crystallized from poly(ethylene glycol) and is essentially homogeneous by sodium dodecylsulfate electrophoresis and isoelectrofocusing. The specific activity of the crystalline preparation was 290 U/mg. The molecular weight was found to be 26000 and the isoelectric point to be 9.8. Amino acid analysis showed 21 aspartic acid or asparagine, 19 threonine, 12 serine, 26 glutamic acid or glutamine, 15 proline, 16 glycine, 14 alanine, 15 valine, 4 methionine, 12 isoleucine, 28 leucine, 7 tyrosine, 7 phenylalanine, 5 histidine, 14 lysine, 16 arginine, 2 tryptophan, no –SS– bonds or free –SH. Guanosine(5′)pentaphospho(5′)adenosine is a very strong inhibitor similar to adenosine(5′)pentaphospho(5′)adenosine as an inhibitor of cytosolic adenylate kinase.

ATP :AMP phosphotransferase has been purified 186-fold from beef heart mitochondria in an overall yield of 30 %. The purified enzyme, M , 31 500, has a specific activity of 800 U/mg and was found to be a homogeneous protein by constancy of specific activity across the elution peak following passage through an Affi-Gel Blue agarose column and by dodecylsulfate gel electrophoresis. Isoelectrofocusing shows a minor peak of activity that arises again when the major peak is re-focused. The p l of the enzyme is 9.30 and the optimum pH of activity is 5.8 in the forward reaction (formation of ADP) and 8.0 in the reverse reaction. The enzyme requires the presence of a divalent metal ion, namely Mg2+, Co2+, Ca2+, Mn2+, Ni2+ and Zn2' in decreasing order of activity and is influenced by NaCl. It shows rigorous specificity for AMP (dAMP) as phosphate acceptor but is rather unspecific for the triphosphate donor since, UTP, CTP, ITP and GTP may substitute for ATP (dATP). ATP and MgATP (dATP was not tested) bind to the enzyme with dissociation constants of 0.122 and 0.132 mM respectively, while AMP (dAMP was not tested), UTP, CTP, ITP and GTP binding could not be detected by the dialysis equilibrium technique used. Amino acid analysis gave the following composition as residues : 26 aspartic acid or asparagine, 14 threonine, 17 serine, 27 glutamic acid or glutamine, 24 proline, 19 glycine, 25 alanine, 17 valine, 8 methionine, 14 isoleucine, 31 leucine, 5 tyrosine, 9 phenylalanine, 6 histidine, 25 lysine, 15 arginine, 4 half cystine (no free sulfhydryls) and no tryptophan, giving a total of 286 residues.The purified mitochondrial adenylate kinase is not a contaminating heart cytosolic enzyme. ATP : AMP phosphotransferase was extracted from beef heart cytosol depleted of mitochondria and brought to homogeneity. Determinations of p1, M , and amino acid composition showed that the heart mitochondrial and cytosolic adenylate kinases are different isozymes.The enzyme (ATP : AMP phosphotransferase is ubiquitous and catalyzes the reaction ATP + AMP + 2 ADP in the presence of specific divalent cations. It has been highly purified from a variety of sources including rabbit muscle [l], porcine muscle [2], porcine liver mitochondria [3], porcine heart mitochondria [4], carp muscle [5], bovine liver mitochondria [6,7], rat Dedicated to Lorenzo Tomasselli on the occasion of his 65th birthday in gratitude for all his contributions to Alfredo.Abbreviations. Mops, 4morpholinepropanesulfonicacid; Hepes, 4-(2-hydroxyethyl)-l-piperazineethanesulfonic acid; Mes, 4-morpholineethanesulfonic acid ; Ap,A, adenosine(5')pentaphospho(5')-adenosine.Enzymes. ATP : AMP phosphotransferase or adenylate kinase or myokinase (EC 2.7.4.3); GTP: AMP phosphotransferase (EC 2.7.4.10); ATPase (EC 3.6.1.3); lactate dehydrogenase (EC 1.1.1.27); pyruvate kinase (EC 2.7.1.40).liver mitochondria [8, 91, rat hepatomas [lo] [14,15], calf muscle and liver [16]. At least two major sets of isozymes, namely the muscle type (skeletal muscle, erythrocytes, and brain) and the liver...

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