enzymes - 10/25/2009 Food Enzymes Love'em and Hate'em...

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10/25/2009 1 Food Enzymes Love’em and Hate’em Enzyme Functions mild conditions • Convert substrate to product • Rapid • Catalytic amounts • Controlled reaction • Non-toxic Christen, Genevieve L. & Smith, J. Scott. 2000
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10/25/2009 2 Christen, Genevieve L. & Smith, J. Scott. 2000 Enzymes are specific, reduce the activation energy, form transient E.S complex; enzyme exits the reaction unchanged, but S is converted to P. Enzymes • Substrate specific Specific to different degrees (pepsin vs • Specific to different degrees (pepsin vs trypsin, chymotrypsin) Table 2.2 Substrate specificity of a legume a-glucosididase Substrate Rel Act % Substrate Rel Act % Belitz maltose 100 Cellobiose 0 amylose 30.9 Phenyl-a- glucoside 3.1 amylopectin 4.4 Phenyl-a- maltoside 29.7
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10/25/2009 3 Enzyme Nomenclature International Union of Biochemistry and Molecular Biology 1. Oxidoreductases: catalyze oxidations or reductions. 2 Transferases catal e a shift of a chemical 2. Transferases: catalyze a shift of a chemical group from a donor to an acceptor substrate. 3. Hydrolases: catalyze the hydrolytic splitting of substrates. 4. Lyases: catalyze the removal or addition of chemical groups to substrates (excluding hydrolysis) Christen, Genevieve L. & Smith, J. Scott. 2000; Belitz hydrolysis). 5. Isomerases: catalyze intramolecular rearrangements. (glucose isomerase) 6. Ligases (synthetases): catalyze combinations of substrate molecules. e.g. Ascorbate oxidase • EC.1.10.3.3 • EC: Enzyme commission • 1. Oxidoreductase • 10. Subclass of oxidoreductase (naming donor of diphenols or ascorbic acid) • 3. Sub class of oxidoreductase (naming oxygen as acceptor) • 3. Serial no. of enzyme within the subclass Christen, Genevieve L. & Smith, J. Scott. 2000
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10/25/2009 4 Multiple forms of enzymes • Isozymes: forms of an enzyme, catalyze the same reaction, differ in physico- chemical characteristics, e.g. pH optima, temperature optima, cation needs, response to inhibitors, pI Belitz Enzyme activity • Expressed under specific conditions (pH, substrate, temp, co factors, ionic strength) • e.g. mol of substrate converted or product formed per unit of time such as min (Units) • e.g mol per unit of time, such as sec (katals (katals) • Specific activity: activity expressed relative to amount of protein present (purity) Belitz
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enzymes - 10/25/2009 Food Enzymes Love'em and Hate'em...

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