Carbonic anhydrase-related proteins

The process of digestion and the activity of carbonic anhydrase are major ev cryday concerns in the medical profession. A clearer understanding of the concepts of protein digestion and carbonic anhydrase acti ity is provid by simplified descriptions of the relevant biochemical mechanisms. Protein digestion involves the addition of water to a peptide bond. Carbonic anhydrase activity involves the addition of water to COj. A related process, the phosphorolysis of glycogen, is also described. 

Zinc is used by a great number of enzymes and proteins, whereas copper seems lobe limited to only a few functions. The most thoroughly studied zinc metailoen-zymes of mammals are carbonic anhydrase, carboxypeptidase A and related pep-... 

Enzymes are proteins that act as catalysts for specific biochemical reactions in living systems. The reactants in enz)une-catalyzed reactions are called substrates. Thousands of vital processes in our bodies are catalyzed by many distinct enzymes. For instance, the enzyme carbonic anhydrase catalyzes the combination of CO2 and water (the substrates), facilitating most of the transport of carbon dioxide in the blood. This combination reaction, ordinarily uselessly slow, proceeds rapidly in the presence of carbonic anhydrase a single molecule of this enzyme can promote the conversion of more than 1 million molecules of carbon dioxide each second. Each enzyme is extremely specific, catalyzing only a few closely related reactions—or, in many cases, only one particular reaction—for only certain substrates. Modern theories of enzyme action attribute this to the requirement of very specific matching of shapes (molecular geometries) for a particular substrate to bind to a particular enzyme (Figure 16-19). 

Randall, W.C., Baldwin, J.J., and Habecker, C.N. (1994) Positions of His-64 and a bound water in human carbonic-anhydrase-II upon binding three structurally related inhibitors. Protein Science, 3,... 

The importance of coordination in the biochemistry of essential metallic elements may be illustrated by numerous examples of metal complexes of which the following are representative the iron complex hemoglobin and numerous enzymes containing the heme and related structures such as catalases, peroxidases and cytochromes and the iron-containing proteins ferritin, transferrin, and hemosiderin the zinc complexes zinc-insulin, carbonic anhydrase and the carboxypeptidases the cobalt complex vitamin B12 the copper complex, ceruloplasmin the molybdenum-containing enzymes, xanthine oxidase, and nitrate reductase DNA-metal ion complexes. 

Deeding very rapidly—the zinc content was from 3 to 18 times the normal. Cruickshank (1936) has surveyed the sources and distribution of zinc in relation to human nutrition, and claims that tuberculosis is associated with a zinc deficiency, and malignant conditions with chronic zinc poisoning. Beri-beri may be due partly to zinc deficiency (Eggleton, 1939). The enzyme carbonic anhydrase is a zinc protein complex. 

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