Global characterization of in vivo enzyme catalytic rates and their correspondence to in vitro k cat measurements

Significance The k cat values of enzymes are important for the study of metabolic systems. However, the current use of k cat presents major difficulties, as values for most enzymes have not been experimentally measured, and experimentally available values are often measured under nonphysiological conditions, thereby casting doubt on the relevance of k cat under in vivo conditions. We present an approach that utilizes omics data to quantitatively analyze the relationship between in vitro k cat values and the maximal catalytic rate of enzymes in vivo. Our approach offers a high-throughput method to obtain enzyme kinetic constants, which reflect in vivo conditions, and are useful for more accurate and complete cellular metabolic models.