Turnover number defines the rate at which an enzyme converts its substrate, usually in terms of the number of substrate molecules that can be converted by a single enzyme molecule and can range from a few molecules to several million molecules per second [1]. The serine protease chymotrypsin cleaves peptide bonds at the rate of 100 molecules per second. In the uncatalyzed reaction, the hydrolysis of peptide bonds in neutral water occurs very slowly, at half rates ranging from 300 to 600 years [2].

Some phosphomonoesterases have the highest known enhancement rate, increasing the reaction rate as much as 1021 times over the uncatalyzed reaction [3, 4]. These include the phosphatases that dephosphorylate phosphoproteins. Rapid phosphorylation and dephosphorylation regulate the charge, conformation, and functionality of proteins enabling cellular processes to be regulated on millisecond time scales. For example, one molecule of tissue non-specific alkaline phosphatase can convert 971 molecules of substrate per second [5, 6]. Without a phosphomonoesterase or other catalyst, the spontaneous hydrolysis of protein phosphoester bond in neutral water at 25 C would otherwise proceed at a half rate exceeding one million years [7, 8]. Other examples of the speed at which enzymes mediate biochemical reactions include DNA and protein synthesis. DNA synthesis occurs at a rate of 50 nucleotides per second in eukaryotes and nearly 1,000 nucleotides per second in some bacteria [9]. Human normoblasts, which comprise less than 0.2% of the total cell mass in the human body, collectively replicate about 4 kilometers of DNA every second [10]. This is nearly 12 times faster than the speed of sound, which travels 0.34 kilometers per second in air. This rate of DNA synthesis, if