Cleavage reactions, single-turnover conditions

For combination in a twin ribozyme both units should specifically interact with a unique substrate sequence. To this end we changed the substrate sequence in the single units and determined the kinetic constants of the cleavage reaction before constructing the twin ribozymes. All single catalytic modules under single turnover conditions had rate constants between 0.2 and 0.5 min-1. 

Schiff base, or quinoidal intermediates do not appreciably affect the rate of the a reaction.90113 (2) L-serine and amino acids such as O-methyl-L-serine that form ES III do stimulate the a reaction.113 (3) The rate of indole-3-glycerol phosphate turnover is roughly correlated with the rate of formation of ES III for each of the amino acids.90-113 (4) The kinetics of the lag in cleavage of indole-3-glycerol phosphate and synthesis of L-tryptophan under single turnover conditions correspond to the rate of ES III formation... 

Rather surprisingly, the hydration of the imidazole carbon and the cleavage of the first carbon—nitrogen bond are relatively rapid reactions. The rate-determining step is located late in the reaction trajectory. It is therefore possible to distinguish at least four optical transients under single turnover conditions. ... 

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