There are many different types of prosthetic groups, including biotin, pyridoxal phosphate, thiamin pyrophosphate, flavin nucleotides and heme. Metallic ions, such as magnesium, copper, iron and zinc, are some of the most common prosthetic groups.
A prosthetic group is a type of cofactor, which is tightly integrated into the enzyme by either covalent or noncovalent forces. Prosthetic groups have a tightly bound nonpolypeptide structure and are required to activate enzymes or other proteins.
Prosthetic groups can be either organic or inorganic. Biotin, flavin nucleotides and pyridoxal phosphate are all examples of organic prosthetic groups, while metallic ions are all inorganic prosthetic groups. Thiamin pyrophosphate, more commonly known as thiamine or vitamin B-1, is another example of an organic phosphate. Pyridoxal phosphate is also a B vitamin, commonly known as pyridoxine or vitamin B-6. Both of these B vitamins are water soluble and supply important parts of a number of different coenzymes.
Heme, which is an ion of iron, is a common inorganic prosthetic group. It is a primary component of hemoglobin, which is the red pigment in blood. Heme is also found in a number of other important hemoproteins, including catalase, cytochrome, myoglobin and endothelial nitric oxide synthase. There are four different types of important hemoproteins: heme A, heme B, heme C and heme O.