Proteins, Enzymes, and Peptide Hormones

Proteins are essential to all living matter and perform numerous functions as cellular components. Fundamental cellular events are catalyMsd by proteins called cn/ymes, while other proteins serve as architectural constituents of protoplasm and cell membranes. Most important arc the classes of hormones that are charactcriitcd us proteins or protein-like compounds because of their polypeplidic. structure. 

Recombinant DNA (rDNA) technology has hod a dramatic impact on our ability to produce complex proteins and polypeptides. structurally identical with those found in vivo. Many of the endogenous proteins or polypeptides have exhibited neurotransmitter and hormonal properties that regulate a variety of important phy.siological procc.s.ses. rDNA-derived technology products currently being used arc discussed below in this chapter. 

Although this chapter reviews the medicinal chemistry of proteins, it includes. some en/.ymology. not only because many drugs affect cnzytrw. systems and vice versa but also because basic discoveries in enzymology have been practically applied to the study of drug-receptor interactions. Hence, a basic introduction to cn/.ymes is included. 

Protein Hydrolysate. Protein hydroly.sate is a solution of amino acids and short-chain oligopeptides that represeni the approximate nutritive equivalent of the ca.sein. lactaibu min. plasma, fibrin, or other. suitable protein from which il is derived by acid, enzymatic, or other hydrolytie method It may be modified by partial removal, and restoration or addition of one or more amino acids. It may contain dextrou or another carbohydrate suitable for intravenous infusion Not less than 50% of the total nitrogen present Ls in the form of o-amino nitrogen. It is a yellowish to rcd-ambet tran.sparent liquid with a pH of 4 to 7. 

In therapeutics, agents affecting volume and compo.sition of body Iluids include various clas.ses of parenteral producLs. Ideally, il would be desirable lo have available parenleral fluids that provide adequate calories and important proteins and lipids lo mimic, as closely as possible, an appropriate diet. Unfortunately, this is not the case. Usually, sufficient earbohydnite is. idminisiered intravenously to prevent ketosis, and in some cases, il is necessary lo give further. sources of carbohydrate by vein lo reduce protein wa.sie. Sources of 

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