Cofactor (biochemistry)

A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's activity as a catalyst, a substance that increases the rate of a chemical reaction.

Sometimes proteins have non-peptide groups attached, which can be called prosthetic groups or cofactors.

For example, the multienzyme complex pyruvate dehydrogenase at the junction of glycolysis and the citric acid cycle requires five organic cofactors and one metal ion: loosely bound thiamine pyrophosphate (TPP), covalently bound lipoamide and flavin adenine dinucleotide (FAD), cosubstrates nicotinamide adenine dinucleotide (NAD + ) and coenzyme A (CoA), and a metal ion (Mg 2+ ). Many contain the nucleotide adenosine monophosphate (AMP) as part of their structures, such as ATP, coenzyme A, FAD, and NAD +.

In biochemistry, flavin adenine dinucleotide (FAD) is a redox-active coenzyme associated with various proteins, which is involved with several important enzymatic reactions in metabolism.

For example, the multienzyme complex pyruvate dehydrogenase at the junction of glycolysis and the citric acid cycle requires five organic cofactors and one metal ion: loosely bound thiamine pyrophosphate (TPP), covalently bound lipoamide and flavin adenine dinucleotide (FAD), cosubstrates nicotinamide adenine dinucleotide (NAD + ) and coenzyme A (CoA), and a metal ion (Mg 2+ ). Many contain the nucleotide adenosine monophosphate (AMP) as part of their structures, such as ATP, coenzyme A, FAD, and NAD +.

Coenzyme A (CoA, SCoA, CoASH) is a coenzyme, notable for its role in the synthesis and oxidation of fatty acids, and the oxidation of pyruvate in the citric acid cycle.

Coenzymes are mostly derived from vitamins and other organic essential nutrients in small amounts. Vitamins can serve as precursors to many organic cofactors (e.g., vitamins B 1, B 2, B 6, B 12, niacin, folic acid) or as coenzymes themselves (e.g., vitamin C).

The B complex vitamins function as enzyme cofactors (coenzymes) or the precursors for them.

Many contain the nucleotide adenosine monophosphate (AMP) as part of their structures, such as ATP, coenzyme A, FAD, and NAD +.

It is also a precursor to DNA and RNA, and is used as a coenzyme.

For example, the multienzyme complex pyruvate dehydrogenase at the junction of glycolysis and the citric acid cycle requires five organic cofactors and one metal ion: loosely bound thiamine pyrophosphate (TPP), covalently bound lipoamide and flavin adenine dinucleotide (FAD), cosubstrates nicotinamide adenine dinucleotide (NAD + ) and coenzyme A (CoA), and a metal ion (Mg 2+ ).

Thiamine pyrophosphate is a cofactor that is present in all living systems, in which it catalyzes several biochemical reactions.

For example, the multienzyme complex pyruvate dehydrogenase at the junction of glycolysis and the citric acid cycle requires five organic cofactors and one metal ion: loosely bound thiamine pyrophosphate (TPP), covalently bound lipoamide and flavin adenine dinucleotide (FAD), cosubstrates nicotinamide adenine dinucleotide (NAD + ) and coenzyme A (CoA), and a metal ion (Mg 2+ ).

Arthur Harden and William Young along with Nick Sheppard determined, in a second experiment, that a heat-sensitive high-molecular-weight subcellular fraction (the enzymes) and a heat-insensitive low-molecular-weight cytoplasm fraction (ADP, ATP and NAD + and other cofactors) are required together for fermentation to proceed.

A cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's activity as a catalyst, a substance that increases the rate of a chemical reaction.

In some enzymes, no amino acids are directly involved in catalysis; instead, the enzyme contains sites to bind and orient catalytic cofactors.

The rates at which these happen are characterized by in an area of study called enzyme kinetics.

These measurements either use changes in the fluorescence of cofactors during an enzyme's reaction mechanism, or of fluorescent dyes added onto specific sites of the protein to report movements that occur during catalysis.

Many contain the nucleotide adenosine monophosphate (AMP) as part of their structures, such as ATP, coenzyme A, FAD, and NAD +.

They carry packets of chemical energy—in the form of the nucleoside triphosphates Adenosine triphosphate (ATP), Guanosine triphosphate (GTP), Cytidine triphosphate (CTP) and Uridine triphosphate (UTP)—throughout the cell to the many cellular functions that demand energy, which include: synthesizing amino acids, proteins and cell membranes and parts, moving the cell and moving cell parts (both internally and intercellularly), dividing the cell, etc. In addition, nucleotides participate in cell signaling (cyclic guanosine monophosphate or cGMP and cyclic adenosine monophosphate or cAMP), and are incorporated into important cofactors of enzymatic reactions (e.g. coenzyme A, FAD, FMN, NAD, and NADP + ).

In humans this list commonly includes iron, magnesium, manganese, cobalt, copper, zinc, and molybdenum.

Cobalt is the active center of a group of coenzymes called cobalamins.

In humans this list commonly includes iron, magnesium, manganese, cobalt, copper, zinc, and molybdenum.

In biology, manganese(II) ions function as cofactors for a large variety of enzymes with many functions.

In humans this list commonly includes iron, magnesium, manganese, cobalt, copper, zinc, and molybdenum.

Enzymes with a zinc atom in the reactive center are widespread in biochemistry, such as alcohol dehydrogenase in humans.

Cofactors can be divided into two major groups: organic Cofactors, such as flavin or heme, and inorganic cofactors, such as the metal ions Mg 2+, Cu +, Mn 2+, or iron-sulfur clusters.

It is in one or the other of these forms that flavin is present as a prosthetic group in flavoproteins.

For example, the multienzyme complex pyruvate dehydrogenase at the junction of glycolysis and the citric acid cycle requires five organic cofactors and one metal ion: loosely bound thiamine pyrophosphate (TPP), covalently bound lipoamide and flavin adenine dinucleotide (FAD), cosubstrates nicotinamide adenine dinucleotide (NAD + ) and coenzyme A (CoA), and a metal ion (Mg 2+ ).

One diverse set of examples is the heme proteins, which consist of a porphyrin ring coordinated to iron.

Many porphyrin-containing metalloproteins have heme as their prosthetic group; these are known as hemoproteins.

Calcium is another special case, in that it is required as a component of the human diet, and it is needed for the full activity of many enzymes, such as nitric oxide synthase, protein phosphatases, and adenylate kinase, but calcium activates these enzymes in allosteric regulation, often binding to these enzymes in a complex with calmodulin.

NOSs are unusual in that they require five cofactors.

Coenzymes are mostly derived from vitamins and other organic essential nutrients in small amounts.

They commonly function as enzymatic cofactors, metabolic regulators or antioxidants.

Cytochromes are proteins containing heme as a cofactor.

This common structure may reflect a common evolutionary origin as part of ribozymes in an ancient RNA world.

For example, the functional part of the ribosome, the biological machine that translates RNA into proteins, is fundamentally a ribozyme, composed of RNA tertiary structural motifs that are often coordinated to metal ions such as Mg 2+ as cofactors.

One diverse set of examples is the heme proteins, which consist of a porphyrin ring coordinated to iron.

One of the best-known families of porphyrin complexes is heme, the pigment in red blood cells, a cofactor of the protein hemoglobin.

Other organisms require additional metals as enzyme cofactors, such as vanadium in the nitrogenase of the nitrogen-fixing bacteria of the genus Azotobacter, tungsten in the aldehyde ferredoxin oxidoreductase of the thermophilic archaean Pyrococcus furiosus, and even cadmium in the carbonic anhydrase from the marine diatom Thalassiosira weissflogii.

A zinc prosthetic group in the enzyme is coordinated in three positions by histidine side-chains.

The complex is a large integral membrane protein composed of several metal prosthetic sites and 14 protein subunits in mammals.

Other organisms require additional metals as enzyme cofactors, such as vanadium in the nitrogenase of the nitrogen-fixing bacteria of the genus Azotobacter, tungsten in the aldehyde ferredoxin oxidoreductase of the thermophilic archaean Pyrococcus furiosus, and even cadmium in the carbonic anhydrase from the marine diatom Thalassiosira weissflogii.

The active site of the AOR family feature an oxo-tungsten center bound to a pair of molybdopterin cofactors (which does not contain molybdenum) and an 4Fe-4S cluster.

Vitamins can serve as precursors to many organic cofactors (e.g., vitamins B 1, B 2, B 6, B 12, niacin, folic acid) or as coenzymes themselves (e.g., vitamin C).

Its active form, pyridoxal 5′-phosphate, serves as a coenzyme in some 100 enzyme reactions in amino acid, glucose, and lipid metabolism.