title: [Two forms of cyclic nucleotide phosphodiesterase and Ca-dependent protein regulator from rabbit skeletal muscles].
abstract: In rabbit skeletal muscle extracts the activity of phosphodiesterase practically insensitive to the increase of Ca2+ concentration from 10(-8) M up to 10(-5) M. The Ca2+-dependent protein regulator is separated from phosphodiesterase at the stage of isolation and purification. The activity of phosphodiesterase devoid of the protein regulator is inhibited by Ca2+ (10(-5)--10(-3) M). An addition of Ca2+-dependent regulator protects the enzyme against inhibition by Ca2+. The Km values for 3',5'-AMP (5 mkM) and 3',5'-GMP (13 mkM) appear to be close; however, the maximal hydrolysis rates for these nucleotides differ considerably (14,0 and 0,25--0,50 nmoles/min/mg of protein). The hydrolysis of 3',5'-AMP is increased 1,6--3,2-fold under the effect of 3',5'-GMP and that of 3',5'-GMP is increased 1,8--2,7-fold under the effect of 3',5'-AMP. Using ion-exchange chromatography it was shown that only 1% of the total activity of skeletal muscle phosphodieterase belongs to the phosphodiesterase sensitive to the activating effect of Ca2+-dependent regulator the activity of this enzymic form is increased 4--5 fold. The Ca2+-dependent regulator of skeletal muscles is inactivated under the effects of trypsin and during gel-filtration is eluted together with the Ca2+-dependent regulator from the heart. The amount of Ca2+-dependent regulator in skeletal muscles is 30 times as low as that in brain and 3 times as low as that in the heart of the rabbit.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000302:isolation & purification / Q000378:metabolism*; D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002147:Calmodulin / Q000302:isolation & purification / Q000378:metabolism* / Q000502:physiology; D004789:Enzyme Activation; D007700:Kinetics; D009132:Muscles / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism; D009928:Organ Specificity; D011817:Rabbits
chemical_list: D002135:Calcium-Binding Proteins; D002147:Calmodulin; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D015106:3',5'-Cyclic-GMP Phosphodiesterases
vernacular_title: Kharakteristika dvukh form fosfodiesterazy tsiklicheskikh nukleotidov i Ca-eavisimogo belkovogo reguliatora v skeletnykh myshtsakh krolika.