Inferring binding rates from enzymatic turnover time statistics

We present a method to extract enzyme-substrate binding rates from observations of enzymatic turnover times. Our approach involves segregating the short-time statistics of the turnover time distribution and inferring from it the binding rate in a general and robust manner. Beyond determining binding rates, the approach developed herein also allows us to infer: (i) the fertile collision probability p , i.e., the probability that a collision between an enzyme and a substrate will result in the formation of an enzyme-substrate complex; and (ii) the fertile catalysis probability ϕ _cat , i.e., the probability that the enzyme-substrate complex will lead to the formation of a product. It has long been known that pϕ _cat ≪ 1, indicating that most enzymes operate far from maximal efficiency, yet separating the contributions of fertile binding and catalysis was not possible in lieu of direct binding rate measurements. Our method overcomes this limitation by enabling precise inference of binding rates from turnover times, which in turn opens the door for a more detailed understanding of enzymatic efficiency.