The effect of temperature on enzymes used in diagnostics

A number of enzymes that are used in clinical analysis have been studied in relation to the effect of temperature on their activity. Both Vmax and Km were determined over a temperature range from 13 to 55 degrees C. Whereas Vmax values increased steadily until denaturation point with all enzymes, the effect of temperature on Km was more variable. With most enzymes there was a gradual increase in Km, often with a sharp rise close to the denaturation temperature. In most cases, Km did not increase as fast as Vmax, consequently the enzyme efficiency, Vmax/Km, also increased slightly with temperature. However this was not the case with rabbit muscle lactate dehydrogenase, for which the Km for pyruvate increased faster than Vmax. As a consequence, it was predicted and confirmed that enzymatic analysis of pyruvate using lactate dehydrogenase is more rapid at 20 degrees C than at 35 degrees C or 50 degrees C.