scholarly journals Alternate substrates of dopamine beta-hydroxylase. I. Kinetic investigations of benzyl cyanides as substrates and inhibitors.

1984 ◽  
Vol 259 (3) ◽  
pp. 1593-1600 ◽  
Author(s):  
G Colombo ◽  
B Rajashekhar ◽  
D P Giedroc ◽  
J J Villafranca
Keyword(s):  
Dopamine Beta Hydroxylase ◽  
Kinetic Investigations

Chromatographic Isolation of the LDH-Isoenzymes of Human Blood Platelets and an Investigation of Their Enzyme Kinetics

1968 ◽  
Vol 20 (03/04) ◽  
pp. 301-313 ◽  
Author(s):  
W Schneider ◽  
K Schumacher ◽  
B Thiede ◽  
R Gross
Keyword(s):  
Human Blood ◽  
Blood Platelets ◽  
Deae Cellulose ◽  
Order Reaction ◽  
Kinetic Properties ◽  
Ldh Isoenzymes ◽  
Kinetic Investigations ◽  
Substrate Concentrations ◽  
Chromatographic Isolation ◽  
Human Blood Platelets

SummaryThe LDH-isoenzymes of human blood platelets show a distinct predominance of the isoenzymes 2 and 3 upon chromatography on DEAE-cellulose. Small amounts of LDH-1 are also present, while only traces of LDH-4 and -5 can be detected.Enzyme kinetic investigations of the principal isoenzymes LDH-1, -2 and -3 clearly show that the differences in inhibition constants with pyruvate as substrate which are demonstrable at 25° largely disappear at 37°. On the other hand, the differences among the isoenzymes in their affinity for pyruvate and lactate as substrate as well as in with respect to the optimal substrate concentrations of pyruvate are more marked at 37° than at 25°. Also, the type of inhibition found with lactate as substrate is increasingly the expression of a higher order reaction in going from LDH-1 to LDH-3. A dependence of the LDH distribution pattern upon the metabolism of the cell is discussed. A comparison of our results with thrombocytes with those of other workers with erythrocytes and leucocytes makes it unlikely that the LDH pattern is directly dependent upon the existence of an oxidative metabolism. Rather, the redox potential of the cell could be of importance for the nature of the pattern of isoenzymes and for their differing kinetic properties.

Kinetic Investigations of Boronized Cold Work Tool Steels

2014 ◽  
Vol 56 (2) ◽  
pp. 104-110 ◽  
Author(s):  
Polat Topuz ◽  
Eren Yılmaz ◽  
Emine Gündoğdu
Keyword(s):  
Cold Work ◽  
Tool Steels ◽  
Kinetic Investigations

scholarly journals Unraveling a Force-Generating Allosteric Pathway of Actomyosin Communication Associated with ADP and Pi Release

2020 ◽  
Vol 22 (1) ◽  
pp. 104
Author(s):  
Peter Franz ◽  
Wiebke Ewert ◽  
Matthias Preller ◽  
Georgios Tsiavaliaris
Keyword(s):  
Structural Changes ◽  
Atp Hydrolysis ◽  
Power Stroke ◽  
Duty Ratio ◽  
Prolonged Duration ◽  
Adp Release ◽  
Strong Transition ◽  
Cleft Closure ◽  
Kinetic Investigations ◽  
Allosteric Pathway

The actomyosin system generates mechanical work with the execution of the power stroke, an ATP-driven, two-step rotational swing of the myosin-neck that occurs post ATP hydrolysis during the transition from weakly to strongly actin-bound myosin states concomitant with Pi release and prior to ADP dissociation. The activating role of actin on product release and force generation is well documented; however, the communication paths associated with weak-to-strong transitions are poorly characterized. With the aid of mutant analyses based on kinetic investigations and simulations, we identified the W-helix as an important hub coupling the structural changes of switch elements during ATP hydrolysis to temporally controlled interactions with actin that are passed to the central transducer and converter. Disturbing the W-helix/transducer pathway increased actin-activated ATP turnover and reduced motor performance as a consequence of prolonged duration of the strongly actin-attached states. Actin-triggered Pi release was accelerated, while ADP release considerably decelerated, both limiting maximum ATPase, thus transforming myosin-2 into a high-duty-ratio motor. This kinetic signature of the mutant allowed us to define the fractional occupancies of intermediate states during the ATPase cycle providing evidence that myosin populates a cleft-closure state of strong actin interaction during the weak-to-strong transition with bound hydrolysis products before accomplishing the power stroke.

scholarly journals The mechanism of inactivation of dopamine beta-hydroxylase by hydrazines.

1986 ◽  
Vol 261 (10) ◽  
pp. 4510-4518 ◽  
Author(s):  
P F Fitzpatrick ◽  
J J Villafranca
Keyword(s):  
Dopamine Beta Hydroxylase

scholarly journals Kinetic and spectroscopic studies of the interaction of copper with dopamine beta-hydroxylase.

1984 ◽  
Vol 259 (6) ◽  
pp. 3395-3398 ◽  
Author(s):  
D E Ash ◽  
N J Papadopoulos ◽  
G Colombo ◽  
J J Villafranca
Keyword(s):  
Spectroscopic Studies ◽  
Dopamine Beta Hydroxylase
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