In molecular biology, the Cofactor transferase family is a family of

protein domain In molecular biology, a protein domain is a region of a protein's Peptide, polypeptide chain that is self-stabilizing and that Protein folding, folds independently from the rest. Each domain forms a compact folded Protein tertiary structure, thre ...

s that includes biotin protein ligases, lipoate-protein ligases A, octanoyl-(acyl carrier protein):protein N-octanoyltransferases, and lipoyl-protein:protein N-lipoyltransferases. The metabolism of the cofactors

Biotin Biotin (also known as vitamin B7 or vitamin H) is one of the B vitamins. It is involved in a wide range of metabolic processes, both in humans and in other organisms, primarily related to the utilization of fats, carbohydrates, and amino acids. ...

and

lipoic acid Lipoic acid (LA), also known as α-lipoic acid, alpha-lipoic acid (ALA) and thioctic acid, is an organosulfur compound derived from caprylic acid (octanoic acid). ALA, which is made in animals normally, is essential for aerobic metabolism. It i ...

share this family. They also share the target modification domain (), and the sulfur insertion enzyme (). Biotin protein ligase (BPL) is the enzyme responsible for attaching biotin to a specific

lysine Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. Lysine contains an α-amino group (which is in the protonated form when the lysine is dissolved in water at physiological pH), an α-carboxylic acid group ( ...

at the

biotin carboxyl carrier protein Biotin carboxyl carrier protein (BCCP) refers to proteins containing a biotin attachment domain that carry biotin and carboxybiotin throughout the Adenosine triphosphate, ATP-dependent carboxylation by biotin-dependent carboxylases. The biotin car ...

. Each organism likely has only one BPL protein. Biotin attachment is a two step reaction that results in the formation of an amide linkage between the carboxyl group of biotin and the epsilon-amino group of the modified lysine. Biotin attachment is required for biotin biosynthesis and utilization of free biotin. Lipoate-protein ligase catalyses the formation of an amide linkage between

and a specific lysine residue of the lipoyl domain of lipoate dependent enzymes. They are required for the utilization of free lipoic acid. Octanoyl-(acyl carrier protein):protein N-octanoyltransferases, or octanoyltransferases, are required for lipoic acid biosynthesis. They transfer octanoate from the acyl carrier protein (ACP), part of fatty acid biosynthesis, to the specific lysine residue of lipoyl domains. Two octanoyltransferase isozymes exist in this superfamily. Lipoyl-protein:protein N-lipoyltransferases, or lipoylamidotransferases, are required for lipoic acid metabolism in some organisms. They transfer lipoic acid or octanoate from lipoyl domains and transfer to other lipoyl domains. In Bacillus subtilis, the transfer is from the glycine cleavage system H protein, GcvH, to other lipoyl domains. This is because the octanoyltransferase of ''B. subtilis'' is specific for GcvH.

Structure

Octanoyltransferases and lipoyl-amidotransferases are single domain enzymes. Characterized lipoate protein ligases require an additional accessory domain () to adenylate the acyl substrate. Biotin protein ligases have an additional C-terminal domain which participates in biotin adenylation and dimerization. Biotin protein ligases may also have an additional N-terminal domain required for DNA binding, although this domain is not always present.

References

{{reflist Protein domains