. Currents in biochemical research, 1956; twenty-seven essays charting the present course of biochemical research and considering the intimate relationship of biochemistry to medicine, physiology, and biology. Biochemistry -- Research. ENZYME KINETICS The initial rate of hydrolysis of urea by urease has been investigated over a 5000-fold range of urea concentration by Kistiakowsky and co-workers. It was found that a four-param- eter equation was required to represent these data, one of the parameters allowing for inhibition at high substrate concentra- tions. The type of three-parameter rate e
. Currents in biochemical research, 1956; twenty-seven essays charting the present course of biochemical research and considering the intimate relationship of biochemistry to medicine, physiology, and biology. Biochemistry -- Research. ENZYME KINETICS The initial rate of hydrolysis of urea by urease has been investigated over a 5000-fold range of urea concentration by Kistiakowsky and co-workers. It was found that a four-param- eter equation was required to represent these data, one of the parameters allowing for inhibition at high substrate concentra- tions. The type of three-parameter rate equation which was found to represent the data at the lower concentrations could be derived by assuming two types of independent active sites, differing in their Michaelis-Menten rate parameters, or pairs of identical sites which interact so that the kinetic parameters of a site are altered when the neighbor site undergoes combination with urea. MECHANISMS OF COENZYME REACTIONS When two substrates are involved in an enzymatic reaction the complexity of the mechanism may be increased considerably. The simplest way in which the Michaelis-Menten mechanism may be elaborated to include a second substrate is E + A , *' - EA (8) EA + B —^ E 4- C -f D The steady-state treatment of this mechanism yields the rate equation 1 + [^2 + ^3(B)]A'i(A) ^'^ Thus the maximum initial velocity will be directly proportional to (B) and the Michaelis constant of A will be a linear function of (B). Chance has found that this rate equation and mechanism represent the data for peroxidase under conditions where only one enzyme-substrate complex must be considered. If one of the products is only slowly dissociated from the enzyme as indicated in the following mechanism E -t- A , ^' ' EA 571. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work
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