[Hexokinase isoenzyme II has a segment responsible for specific interaction of the enzyme with mitochondrial membranes]. / II izozim geksokinazy imeet uchastok, otvetstvennyi za spetsificheskoe vzaimodeistvie fermenta s mitokhondrial'nymi membranami.

It was found that the ability of rat skeletal muscle hexokinase isozyme II binding to mitochondrial membranes is realized in full in the presence of Mg2+, glucose and putrescine as adsorption reagent. The hexokinase-membrane complexes obtained through the use of these reagents displayed similar stability as could be judged from their dissociation under identical conditions: either in the presence of KCl used in high concentrations or under the effect of a specific solubilization reagent--glucose-6-phosphate used in physiological concentrations. Within the composition of enzyme-membrane complexes hexokinase had the same kinetic properties which differed, however, from those of the nonbound to mitochondria enzyme. The data obtained are discussed in relation to the hexokinase isozyme II domain responsible for the specific binding of the enzyme to mitochondrial membranes and termed as the "adsorption domain". The availability of this domain is postulated in terms of the concept on the adsorption mechanism of hexokinase isozyme II activity control in skeletal muscles.

[Solubilization of mitochondria-bound rat skeletal muscle hexokinase isoenzyme II by glucose-6-phosphate]. / Soliubilizatsiia sviazannogo s mitokhondriiami i izozima geksokinazy skeletnykh myshts krysy pod deistviem gliukozo-6-fosfata.

Solubilization of bound to outer mitochondrial membrane hexokinase isoenzyme II by glucose-6-phosphate (G-6-P) has been studied. Dissociation of the enzyme-membrane complex was analyzed in both active (in the presence of reaction substrates) and inactive states. The magnitude of the complex dissociation constants was determined under G-6-P action in the presence and absence Mg.ATP. Besides, some kinetic parameters of hexokinase isoenzyme II in its free and bound forms were estimated. It is suggested that the mechanism of dissociation of the hexokinase-membrane complex by G-6-P is coupled with the kinetic mechanism of the reaction catalyzed by hexokinase isoenzyme II.

[Kinetic characteristics of creatine kinase and hexokinase from rat skeletal muscles during dietary deficit of vitamin K and administration of pelentane]. / Kineticheskie kharakteristiki kreatinkinazy i geksokinazy skeletnykh myshts krysy pri pishchevom defitsite vitamina K i vvedenii pelentana.

Kinetic parameters of rat creatine kinase isozymes at different vitamin K supply and treatment with antivitamin K--pelentan have been determined. MM-isozyme (skeletal muscle) has selective sensitivity to the vitamin K deficit, while BB and MB-isozymes (brain, kidney and heart) have not. The value KM for ATP of MM-isozymes increases, while maximal activity decreases. Pelentan treatment does not lead to the change of MM-creatine kinase affinity to ATP. Soluble hexokinase of skeletal muscle in rats with vitamin K deficiency and treated with pelentan has higher affinity to glucose as compared to normal rat enzyme. It has been supposed that skeletal muscle hexokinase exists in a particular molecular form under vitamin K deficiency.

[Preparation of hexokinase isoenzyme II with expressed adsorption properties]. / Poluchenie izozima II geksokinazy s vyrazhennymi adsorbtsionnymi svoistvami.

The isolation of the native hexokinase isozyme II possessing a high adsorptive capacity is described. This property underlies the adsorption mechanism responsible for the control of the hexokinase activity in the cell and is realized only under conditions of the structural integrity of the enzyme. The latter is due, primarily, to the functional state of the specific adsorption domain which provides the specific interaction of hexokinase isozyme II with biological membranes. The criteria of nativity of skeletal muscle hexokinase were elaborated. A procedure for obtaining highly purified native hexokinase isozyme II from rat skeletal muscle was developed.