scholarly journals Evidence for the Presence of Two Kinetically Distinct Active Forms of Ribonuclease T2. The pH Dependence of the Steady-State Kinetic Parameter, kcat, for Transphosphorylation of Both a Natural and a Synthetic Substrate

1981 ◽  
Vol 114 (2) ◽  
pp. 229-234 ◽  
Author(s):  
Toshihiro YASUDA ◽  
Yasuo INOUE
Keyword(s):  
Steady State ◽  
Kinetic Parameter ◽  
Ph Dependence ◽  
Synthetic Substrate ◽  
Steady State Kinetic ◽  
State Kinetic

A Kinetic Method for Characterization of Heterogenous Fibrinogen and Its Application to Fibrinogen Grand Rapids, a Congenital Dysfibrinogenemia

1982 ◽  
Vol 48 (02) ◽  
pp. 182-186 ◽  
Author(s):  
D L Higgins ◽  
S D Lewis ◽  
J A Penner ◽  
J A Shafer
Keyword(s):  
Steady State ◽  
Kinetic Parameter ◽  
Kinetic Analysis ◽  
Kinetic Method ◽  
Plasma Fibrinogen ◽  
Normal Value ◽  
Steady State Kinetic ◽  
Grand Rapids ◽  
State Kinetic

SummaryA kinetic analysis was developed to determine the steady state kinetic parameter kcat/KM for the thrombin-catalyzed release of FPA from abnormal and normal fibrinogen in mixtures of the two. Such mixtures are likely to comprise the fibrinogen of individuals with congenital dysfibrinogenemia. The analysis was used to characterize fibrinogen Grand Rapids, a new congenital dysfibrinogenemia. It indicated that fibrinogen from affected individuals was composed of normal and abnormal fibrinogen in roughly equal amounts, and that the value of kcat/KM for the thrombin-catalyzed release of FPA from the fibrinogen variant was 77fold lower than that for the release of FPA from the normal fibrinogen. In separate studies, fibrinogen Grand Rapids was found to exhibit a reduced clottability. Additionally, affected individuals appeared to have plasma fibrinogen concentrations which were about one-third the normal value.

scholarly journals Variation in the pH-dependent pre-steady-state and steady-state kinetic characteristics of cysteine-proteinase mechanism: evidence for electrostatic modulation of catalytic-site function by the neighbouring carboxylate anion

2003 ◽  
Vol 372 (3) ◽  
pp. 735-746 ◽  
Author(s):  
Syeed HUSSAIN ◽  
Surapong PINITGLANG ◽  
Tamara S. F. BAILEY ◽  
James D. REID ◽  
Michael A. NOBLE ◽  
...  
Keyword(s):  
Steady State ◽  
Cysteine Proteinase ◽  
Ph Dependence ◽  
Catalytic Site ◽  
Rate Determining Step ◽  
Steady State Kinetic ◽  
Pka Value ◽  
Site Function ◽  
Hydrolysis Of ◽  
State Kinetic

The acylation and deacylation stages of the hydrolysis of N-acetyl-Phe-Gly methyl thionoester catalysed by papain and actinidin were investigated by stopped-flow spectral analysis. Differences in the forms of pH-dependence of the steady-state and pre-steady-state kinetic parameters support the hypothesis that, whereas for papain, in accord with the traditional view, the rate-determining step is the base-catalysed reaction of the acyl-enzyme intermediate with water, for actinidin it is a post-acylation conformational change required to permit release of the alcohol product and its replacement in the catalytic site by the key water molecule. Possible assignments of the kinetically influential pKa values, guided by the results of modelling, including electrostatic-potential calculations, and of the mechanistic roles of the ionizing groups, are discussed. It is concluded that Asp161 is the source of a key electrostatic modulator (pKa 5.0±0.1) in actinidin, analogous to Asp158 in papain, whose influence is not detected kinetically; it is always in the ‘on’ state because of its low pKa value (2.8±0.06).

Human liver aldehyde reductase: pH dependence of steady-state kinetic parameters

1991 ◽  
Vol 287 (2) ◽  
pp. 329-336 ◽  
Author(s):  
Aruni Bhatnagar ◽  
Ballabh Das ◽  
Si-Qi Liu ◽  
Satish K. Srivastava
Keyword(s):  
Steady State ◽  
Kinetic Parameters ◽  
Human Liver ◽  
Ph Dependence ◽  
Aldehyde Reductase ◽  
Steady State Kinetic ◽  
State Kinetic
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