2.3 Most enzymes are proteins 2.3. 1 Some enzymes require no other chemical groups other than their amino acid residues for activity. (e.g) 2.3.2 Other enzymes require additional chemical components called prosthetic groups(covalently bound) (or cofactors). 2.3.3 Prosthetic groups could be inorganic metal ions(e.g, Fe2+, Mg2+, Mn2+, Zn2+)or complex organic or metalloorganic molecules called coenzymes 2.3. 4 a complete catalytically active enzyme (including its prosthetic group) is called a holoenzyme 2.3.5 The protein part of an enzyme(without its prosthetic group) is called the apoenzyme
2.3 Most enzymes are proteins. 2.3.1 Some enzymes require no other chemical groups other than their amino acid residues for activity. (e.g.) 2.3.2 Other enzymes require additional chemical components called prosthetic groups (covalently bound) (or cofactors). 2.3.3 Prosthetic groups could be inorganic metal ions (e.g., Fe2+, Mg2+, Mn2+, Zn2+) or complex organic or metalloorganic molecules called coenzymes. 2.3.4 A complete catalytically active enzyme (including its prosthetic group) is called a holoenzyme. 2.3.5 The protein part of an enzyme (without its prosthetic group) is called the apoenzyme
2.3.6 Coenzymes often function as transient carriers of specific(functional groups during catalysis 2.3.7 Many vitamins, organic nutrients required in small amounts in the diet, are precursors of coenzymes
2.3.6 Coenzymes often function as transient carriers of specific (functional) groups during catalysis. 2.3.7 Many vitamins, organic nutrients required in small amounts in the diet, are precursors of coenzymes
able 8-5 Some Rate Enhancements produced by Enzymes Cyclophilin 10 Carbonic anhydrase 10 Triose phosphate isomerase 10 Carboxypeptidase A 10 Phosphoglucomutase 1012 Succinyl-CoA transferase 1013 Urease 1014 Orotidine monophosphate decarboxylase 10
table 8-1 Some Inorganic Elements That Serve as Cofactors for Enzymes C Cytochrome oxidase Fe Cytochrome oxidase, catalase, peroxidase Pyruvate kinase Hexokinase, glucose 6-phosphatase, pyruvate kinase M Arginase, ribonucleotide reductase Mo Dinitrogenase Urease Se Glutathione peroxidase Zn Carbonic anhydrase, alcohol dehydrogenase, carboxypeptidases A and B
table 8-2 Some Coenzymes That Serve as Transient Carriers of Specific Atoms or Functional groups* Examples of chemical Dietary precursor in Coenzyme groups transferred mammaLs Biocytin Biotin Coenzyme A Acyl groups Pantothenic acid and other compounds 5-Deoxyadenosylcobalamin H atoms and Vitamin B 12 coenzyme B12) alkyl groups Flavin adenine dinucleotide Electrons Riboflavin(vitamin B2) Lipoate Electrons and Not required in diet acyl groups Nicotinamide adenine Hydride ion(: H Nicotinic acid(niacin) dinucleotide yridoxal phosphate Amino groups Pyridoxine (vitamin B6) Tetrahydrofolate One-carbon groups Folate Thiamine pyrophosphate Aldehydes Thiamine (vitamin B,) "The structure and mode of action of these coenzymes are described in Part Ill of this book