Prosthetic Groups Are Tightly Integrated Into an Enzymes Structure

Prosthetic groups are distinguished by their tight, stable incorporation into a protein's structure by covalent or noncovalent forces. Examples include pyridoxal phosphate, flavin mononucleotide (FMN), flavin dinu-cleotide (FAD), thiamin pyrophosphate, biotin, and the metal ions of Co, Cu, Mg, Mn, Se, and Zn. Metals are the most common prosthetic groups. The roughly one-third of all enzymes that contain tightly bound metal ions are termed metalloenzymes. Metal ions that participate in redox reactions generally are complexed to prosthetic groups such as heme (Chapter 6) or iron-sulfur clusters (Chapter 12). Metals also may facilitate the binding and orientation of substrates, the formation of covalent bonds with reaction intermediates (Co2+ in coenzyme B12), or interaction with substrates to render them more electrophilic (electron-poor) or nucleo-philic (electron-rich).

2. Transferases catalyze transfer of groups such as methyl or glycosyl groups from a donor molecule to an acceptor molecule.

3. Hydrolases catalyze the hydrolytic cleavage of C— C, C— O, C—N, P— O, and certain other bonds, including acid anhydride bonds.

4. Lyases catalyze cleavage of C— C, C— O, C—N, and other bonds by elimination, leaving double bonds, and also add groups to double bonds.

5. Isomerases catalyze geometric or structural changes within a single molecule.

6. Ligases catalyze the joining together of two molecules, coupled to the hydrolysis of a pyrophospho-ryl group in ATP or a similar nucleoside triphos-phate.

Despite the many advantages of the IUB system, texts tend to refer to most enzymes by their older and shorter, albeit sometimes ambiguous names.

Diabetes 2

Diabetes 2

Diabetes is a disease that affects the way your body uses food. Normally, your body converts sugars, starches and other foods into a form of sugar called glucose. Your body uses glucose for fuel. The cells receive the glucose through the bloodstream. They then use insulin a hormone made by the pancreas to absorb the glucose, convert it into energy, and either use it or store it for later use. Learn more...

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