Light-flash analysis of the photoenzymic repair process in yeast cells. II. Determination of the rate constant for formation of photoreactivating enzymes-pyrimidine dimer complexes and its activation energy term.

As reported in the previous paper, the number of deoxyribodipyrimidine photolyase or photoreactivating enzyme (PRE) molecules per yeast cell was determined by the use of intense light flashes. In the present work, the reaction rate constant for the formation of PRE-substrate complexes, k1, and the activation energy term of k1 were determined by yeast cells in vivo by the use of light flashes. At 30 degrees C, k1 equalled (6.5 +/- 1.1) x 10(-5) (nuclear volume) x (molecule)(-1) sec(-1), which corresponded to 1.1 x 10(5) 1 mole(-1) sec(-1), on the assumption that a nuclear volume is 3 x 10(-15) 1. k1 showed positive temperature dependence as described by the arrhenius expression with an activation energy of 11.8 +/- 1.6 kcal mole(-1).