| Comments |
The turnover number of an enzyme,
is the number of substrate molecules converted into product by an enzyme molecule
in a unit time when the enzyme is fully saturated with substrate. The turnover numbers of most enzymes
with their physiological substrates fall in the range from 1 to 10^4 per second
(Table link). Range 0.5 sec^-1 (lysozyme) - 600,000 sec^-1(carbonic anhydrase). The turnover number depends on temperature. This can nbe seen in Arrhenius law, which describes the rate of chemical reactions: k=Ae^-[(Ea)/RT] where k is the rate constant, A is the pre-exponential factor or simply the prefactor, Ea is the activation energy, R is the gas constant and T is the temperature. T is in the denominator of the exponent, meaning that increase in temperature increases the rate. See order of magnitude increase in turnover number of sodium-hydrogen antiporter between 22°C (BNID 105479) and 37°C (BNID 105481), see comments section in these BNIDs. |