pantetheine

Pantetheine is a small organosulfur molecule that consists of pantothenic acid linked to cysteamine by an amide bond. It contains a terminal thiol group derived from cysteamine, which is the reactive site for thioester formation. Pantetheine is best known as the pantetheine moiety of coenzyme A (CoA). In cells, CoA contains a pantetheine group attached to an adenosine diphosphate unit, and the thiol group of pantetheine forms high-energy thioester bonds with acyl groups, enabling key transfer reactions in metabolism.

Biological role and significance arise from its place in CoA biosynthesis and function. Pantothenate (vitamin B5) is converted through a short biosynthetic pathway to 4'-phosphopantetheine, which is then incorporated into CoA. The 4'-phosphopantetheine prosthetic group is essential for the activity of several carrier proteins, notably the acyl carrier protein (ACP) involved in fatty acid synthesis, and for the catalytic roles of CoA-dependent enzymes. The ability of the pantetheine moiety to form and transfer acyl groups underpins central metabolic processes such as fatty acid synthesis, the citrate cycle, and the regulation of energy metabolism.

In summary, pantetheine functions primarily as a precursor and component of CoA, providing the reactive thiol that forms and transfers acyl groups in numerous biochemical pathways. Its relevance extends to the activation of carrier proteins via 4'-phosphopantetheinylation and to the broad role of CoA as a central acyl group carrier in metabolism.