The Structure And Function Of Enzymes

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Enzyme structure and function Enzymes are three-dimensional globular proteins that exist as a tertiary structure. The shape comes from the proteins primary structure, (the specific sequence of amino acids that form the protein) and its secondary structure. Their function is determined by their complex shape. In globular proteins the 3D shape usually has hydrophobic amino acid R-groups in the centre of the “ball” and hydrophilic amino acid R-groups around the outside of the ball. The amino acid chain spirals, pleats and turns to form the overall structure. (Fullick, A. 2000) The overall folding or tertiary structure provides structural scaffolding that presents catalytically essential amino acids and cofactors in a specific special orientation to facilitate catalysis. (Copeland, R.A. 2005). Enzymes are formed during transcription. During transcription, DNA unwinds to reveal a gene that codes for the production of an enzyme. A transcript called messenger RNA is produced from the code held in the gene. The messenger RNA leaves the nucleus via a nuclear pore and binds to a ribosome. The messenger RNA strand is then used to build up a precise sequence of amino acids. One amino acid is bound to another when a condensation reaction occurs, creating a polypeptide chain, or the primary structure of an enzyme. (Class notes, 2011). Figure 1 explains the primary, secondary and tertiary structure. The Primary structure is the order in which the amino acids (peptides) are covalently linked together. (Copeland, R.A. 2005) It is the one dimensional first step in specifying the three-dimensional structure of an enzyme. Peptide bonds are formed by a process called condensation. This is the joining of molecules by the removal of water and involves removing a hydroxide group from one of the molecules and a hydrogen bond from the other molecule. (P, Champe. 2005). The Secondary
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