coenzyme

Examples of coenzyme in the following topics:

• Control of Metabolism Through Enzyme Regulation

  • Many enzymes only work if bound to non-protein helper molecules called cofactors and coenzymes.
  • Coenzymes are organic helper molecules with a basic atomic structure made up of carbon and hydrogen.
  • The most common coenzymes are dietary vitamins.
  • The availability of various cofactors and coenzymes regulates enzyme function.
  • Vitamins are important coenzymes or precursors of coenzymes and are required for enzymes to function properly.

• Cofactors and Energy Transitions

  • They can also be classified depending on how tightly they bind to an enzyme, with loosely-bound cofactors termed coenzymes and tightly-bound cofactors termed prosthetic groups.
  • Many contain the nucleotide adenosine monophosphate (AMP) as part of their structures, such as ATP, coenzyme A, FAD, and NAD+.
  • Vitamins can serve as precursors to many organic cofactors (e.g., vitamins B1, B2, B6, B12, niacin, folic acid) or as coenzymes themselves (e.g., vitamin C).
  • Many organic cofactors also contain a nucleotide, such as the electron carriers NAD and FAD, and coenzyme A, which carries acyl groups.
  • These group-transfer intermediates are the loosely-bound organic cofactors, often called coenzymes.

• Energy Conservation and Autotrophy in Archaea

  • Methanogenesis uses a range of coenzymes that are unique to these archaea, such as coenzyme M and methanofuran.

• Pyruvic Acid and Metabolism

  • Pyruvate is converted into acetyl-coenzyme A, which is the main input for a series of reactions known as the Krebs cycle.
  • Pyruvate from glycolysis is converted by fermentation to lactate using the enzyme lactate dehydrogenase and the coenzyme NADH in lactate fermentation.

• Types of Catabolism

  • Next, these smaller molecules are taken up by cells and converted to yet smaller molecules, usually the acetyl coenzyme A (acetyl-CoA), which releases some energy.
  • Finally, the acetyl group on the CoA is oxidized to water and carbon dioxide in the citric acid cycle and electron transport chain, releasing the energy that is stored by reducing the coenzyme nicotinamide adenine dinucleotide (NAD+) into NADH.
  • An alternative route for glucose breakdown is the pentose phosphate pathway, which reduces the coenzyme NADPH and produces pentose sugars such as ribose, the sugar component of nucleic acids.

• Methanogenesis

  • It involves the coenzymes and cofactors F420, coenzyme B, coenzyme M, methanofuran, and methanopterin.

• Citric Acid and Other Organic Compounds

  • It is produced from acetyl coenzyme A and oxaloacetate in the presence of the enzyme citrate synthase.

• Carboxysomes

  • Similar structures are known to harbor the B12-containing coenzyme glycerol dehydratase, the key enzyme of glycerol fermentation to 1,3-propanediol, in some Enterobacteriaceae, such as Salmonella.

• Breakdown of Pyruvate

  • In order for pyruvate, the product of glycolysis, to enter the next pathway, it must undergo several changes to become acetyl Coenzyme A (acetyl CoA).

• Biosynthetic Mechanisms

  • The thiol portion of the thioester is usually a protein of some kind, with efficient acetyl transport occurring by way of acetyl coenzyme A.
  • The reduction steps (designated by [H] in the equations) and the intervening dehydrations needed for fatty acid synthesis require unique coenzymes and phosphorylating reagents.