tailieunhanh - Enzyme structure and function

Enzymes are proteins that catalyze chemical reactions. A protein is simply a polypeptide composed of amino acids linked by a peptide bond, and the term generally, but not always, refers to the folded conformation. To understand how an enzyme functions, including its binding and functional properties, it is necessary to know the properties of the amino acids and how the amino acids are linked together, including the torsion angles of the bonds and the space occupied, and the interactions of the atoms leading to the final conformations of the folded protein. Only in the folded state can a protein function effectively as an enzyme to bind substrates. | 1 Enzyme Structure and Function Edward A. Meighen CONTENTS Introduction Primary Structure Van der Waals Interactions Hydrogen and Ionic Bonds Hydrophobic Interactions Peptide Bonds Secondary Structure Torsion Angles Ramachandran Plot -Helixes -Sheets Reverse Turns and Loops Prediction of -Helixes -Sheets and Reverse Turns in Peptide Sequences Prediction of the Hydropathy or Polarity of Peptide Sequences Folding of the Protein into Specific Conformations Tertiary Structure Quaternary Structure Posttranslational Modification Structural Classification Enzyme Classification by Function Enzymes and Active Sites Cofactors Enzyme Interactions with Substrates and Cofactors Tyrosyl tRNA Synthetase Human Aldose Reductase Dihydropteroate Synthase DOPA Decarboxylase Measurement of Enzyme Ligand Interactions . Independent Binding Sites Allosteric Behavior Homotropic Interactions 2005 by CRC Press Allosteric Interactions between Two Different Ligands Heterotropic Interactions Specificity Protein Engineering and Drug Design Acknowledgments Bibliography INTRODUCTION Enzymes are proteins that catalyze chemical reactions. A protein is simply a polypeptide composed of amino acids linked by a peptide bond and the term generally but not always refers to the folded conformation. To understand how an enzyme functions including its binding and functional properties it is necessary to know the properties of the amino acids and how the amino acids are linked together including the torsion angles of the bonds and the space occupied and the interactions of the atoms leading to the final conformations of the folded protein. Only in the folded state can a protein function effectively as an enzyme to bind substrates and act as a catalyst. The structural organization of a protein is generally classified into four categories