Hydrolase

Hydrolases are hydrolytic enzymes, biochemical catalysts that use water to cleave chemical bonds, usually dividing a large molecule into two smaller molecules. Examples of common hydrolases include esterases, proteases, glycosidases, nucleosidases, and lipases.

Hydrolases carry out important degradative reactions in the body. During digestion, lipases hydrolyze lipids and proteases convert protein to amino acids. Hydrolases cleave large molecules into fragments used for synthesis, the excretion of waste materials, or as sources of carbon for the production of energy. In these reactions, many biopolymers are converted to monomers. Some hydrolases release energy as they act.

One of the most important hydrolases is acetylcholine esterase (cholinesterase). Acetylcholine is a potent neurotransmitter for voluntary muscle. Nerve impulses travel along neurons to the synaptic cleft, where acetylcholine stored in vesicles is released, carrying the impulse across the synapse to the postsynaptic neuron and propagating the nerve impulse. After the nerve impulse moves on, the action of the neurotransmitter molecules must be stopped by cholinesterase, which hydrolyzes acetylcholine to choline and acetic acid. Some dangerous toxins such as the exotoxin of Clostridium botulinum and saxitoxin interfere with cholinesterase, and many nerve agents such as tabun and sarin act by blocking the hydrolytic action of cholinesterase.

Bibliography

Devlin, T. M. (2002). Textbook of Biochemistry, 5th edition. New York: John Wiley.

McKee, T., and McKee, J. R. (2003). Biochemistry, 3rd edition. Boston: McGraw-Hill.

Voet, D., Voet, J. G., and Pratt, C. W. (2002). Biochemistry, 2nd edition. New York: John Wiley.