9319354 Pezzementi Whenever one moves a muscle, the enzyme acetylcholinesterase insures that the muscle will relax by breaking down the neurotransmitter acetylcholine, which is released by the nervous system initiating the processes of muscle contraction. Thus, acetylcholinesterase is required for all motor activity, including writing and speech. In addition to acetylcholinesterase, humans possess another evolutionarily related enzyme, butyrylcholinesterase, with similar, but distinct, characteristics. In contrast to acetylcholinesterase, the function of this enzyme is unknown. In fact, there appear to be individuals who lack this enzyme entirely, yet appear normal. It has been suggested that butyrylcholinesterase acts as a scavenger of ingested neurotoxins and that it plays a role in the embryological development of the nervous system. Although humans and other higher vertebrates possess both cholinesterases, lower vertebrates appear to possess only one, acetylcholinesterase. Invertebrates also possess only one cholinesterase; however, it is neither acetylcholinesterase, nor butyrylcholinesterase, but an enzyme with intermediate characteristics. It has been stated that "nothing in biology makes sense, except in the light of evolution." Thus, in an attempt to clarify the roles of the two cholinesterases in humans, in particular butyrylcholinesterase, Dr. Pezzementi is tracing the evolution of the two enzymes, using the techniques of biochemistry, pharmacology, and recombinant DNA technology to study the structure and function of cholinesterases in selected organisms, where the transition from a single intermediate cholinesterase to two distinct cholinesterases occurs. Integration of this information with the biology of the organisms in question could provide further clues about the physiological functions of these enzymes. ***
