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Biomedical subjects

D C Watts

Publications and source records attributed to D C Watts.

At least 199 records · Page 11Linked to original sources
PubMed1968

Formation of an unusual hybrid in the development of human adenosine 5'-triphosphate-creatine phosphotransferase.

1. Starch-gel analysis of extracts from adult human muscle, heart and brain reveals a hybrid creatine kinase with an abnormally high electrophoretic mobility. 2. Hybridization in vitro confirms that the postulated hybrid is formed from a combination of brain- and muscle-type enzyme sub-units. 3. The relative electrophoretic mobility of the hybrid is not affected by changing the starch concentration in the gel or by the buffer system used, or by electrophoresis in thin layers of Sephadex. 4. It is concluded that hybrid formation results in a net increase on the dimeric enzyme of from 4 to 6 negative charges. 5. During development a sharp increase in the rate of production of muscle-type enzyme sub-units occurs in heart at 10-13 weeks' gestation and in muscle at 18-20 weeks' gestation. The latter change is accompanied by a relative decrease in the concentration of brain-type sub-units.

Adenosine Triphosphate↗
PubMed1966

The chemistry of xanthine oxidase. Reaction with iodoacetamide.

1. The reaction of milk xanthine oxidase with iodoacetamide has been studied with the silver-silver iodide electrode. 2. The reaction proceeds considerably faster in the presence of xanthine than in its absence. Anaerobically, with excess of xanthine, the reaction takes place as a rapid phase in which the enzyme is inactivated and in which approx. 1 thiol group/mol. of enzyme reacts and as a slower phase in which about 12 groups/mol. react. 3. The rapid reaction appears to be first-order with respect to xanthine oxidase and iodoacetamide and independent of the xanthine concentration with more than about 3mol. of xanthine/mol. of enzyme. 4. The velocity constant of the rapid phase is 0.26min.(-1) at 25 degrees and pH7.0, with 1mm-iodoacetamide and 17mum-xanthine oxidase. The velocity constant for the slower phase is about one-hundredth of this value. 5. The velocities of both phases increase with increasing pH in the range 5.0-9.6. 6. Xanthine may be replaced by salicylaldehyde without affecting the rate of loss of enzymic activity. With sodium dithionite as reducing agent, the reaction is slightly faster. 7. The possible function of thiol groups in the reaction mechanism of the enzyme is discussed.

Aldehydes↗
PubMed1966

Adenosine 5'-triphosphate-arginine phosphotransferase from lobster muscle. Molecular weight.

1. The molecular weight of arginine kinase from lobster muscle has been determined by three procedures: ultracentrifuge analysis, gel filtration and density-gradient centrifugation. 2. The three methods give similar results and the best estimate of the molecular weight is 37000. 3. The enzyme does not readily show association-dissociation phenomena. 4. The usefulness of density-gradient centrifugation for determinations of molecular weight is briefly discussed.

Animals↗
PubMed1966

The role of thiol groups in the structure and mechanism of action of arginine kinase.

1. A detailed study of the reaction of iodoacetamide with arginine kinase has been carried out. 2. The enzyme contains five reactive thiol groups per 37000g. of protein, all of which can be alkylated. 3. Below pH8.5 loss of activity is substantially independent of pH and can be correlated with the alkylation of a single pH-independent thiol. 4. One catalytic site per enzyme molecule is inferred. 5. The progress curves of the alkylation reaction are polyphasic and reveal a pH-and time-dependent sequential release of thiols which is dependent upon the alkylation of the first pH-independent thiol. This is supported by electrophoretic investigations. 6. Comparison of alkylation rate and rate of loss of activity suggests that two thiol groups are not essential for catalytic activity. Variability in enzyme preparations with respect to alkylation rate appears to be associated with these two groups. 7. A complex protection pattern is revealed by the effects of various substrate combinations on rates of alkylation and of loss of activity. It is inferred that two thiol groups participate in conformational changes and nucleotide interactions. 8. Comparison with creatine kinase suggests a fundamentally similar catalytic mechanism, although for arginine kinase certain additional restrictions are necessary because of the protection observed with nucleotide substrates.

Adenine Nucleotides↗
PubMed1966

Adenosine 5 -triphosphate--creatine phosphotransferase from dystrophic mouse skeletal muscle. A genetic lesion associated with the catalytic-site thiol group.

1. A column procedure for the purification of creatine kinase from normal and dystrophic mouse muscle is described. 2. The native enzymes are indistinguishable by various physical criteria and have mol.wt. about 80000. 3. The purified enzyme from dystrophic muscle is only half as active as the normal, contains only one thiol group readily alkylated by iodoacetamide instead of two and has one less free thiol group/mol. 4. Michaelis constants for MgATP and creatine are the same for both preparations. 5. The inhibitor constant for ADP at pH9.0 is different in the two enzymes and this may account for the different degrees of inhibition observed in vitro with the drug Laevadosin. 6. The enzyme from dystrophic muscle is protected by an equilibrium mixture of substrates against inhibition by iodoacetamide to a greater extent than the normal enzyme. 7. ;Fingerprinting' suggests one peptide difference between creatine kinases from normal and dystrophic muscle. 8. The possibility that this finding represents the primary lesion in dystrophy is discussed.

Animals↗