Fluorohydrolase enhancement ratios

To compare the catalytic efficiency of catalysts, it is helpful to compare the enhancement ratios (E.R.). E.R. is calculated by dividing the kcat by the kuncat (the rate constant for the uncatalyzed reaction). Enormous rate enhancements are achieved by enzymes. For example, hydrolytic enzymes often exhibit rate enhancements of 10 -10 2 compared with the spontaneous water-catalyzed or the acid/base-catalyzed reaction at about neutral pH. e For purposes of comparison, the kcat, kuncat, and E.R. values for two hydrolytic abzymes, as well as CCMP fluorohydrolase chromatographed on G-15 Sephadex gel is presented in Table 3. The fluorohydrolase, chromatographed on G-15 Sephadex, has an E.R. four times that of the two abzymes. In addition, the enhancement ratios of natural DFPases from various sources as well as CCMP fluorohydrolase are presented in Table 4. In all cases, the initial E.R. (before any purification) is higher for semisynthetic fluorohydrolases than for any of the natural unpurified DFPases. 

Table 3. Comparison of semisynthetic enhancement ratios of fluorohydrolases. abzymes and...

Table 4. Comparison of enhancement ratios of natural DFPases and CCMP fluorohydrolases. 

Semisynthetic fluorohydrolase has activity comparable to the naturally occurring DFPases and does not require a divalent cation as does the "Mazur-type" enzyme. It operates over a pH range from 6.5 to 8.0 with the optimum at approximately 7.5. A comparison of natural and semisynthetic fluorohydrolase activity is shown in Table 4. An examination of the enhancement ratio (2.2 x 10 ) shows that the CCMP fluorohydrolase is a remarkably good catalyst. If the crosslinking reaction is further optimized to increase the yield of the dimer along with further purification steps, a stable highly efficient semisynthetic fluorohydrolase should be achieved. 

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See also in sourсe #XX -- [ ]

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