Biotin holoenzyme synthetase

Biotin becomes attached to the proper e-amino groups at the active centers of biotin enzymes by the action of biotin holoenzyme synthetase (biotinyl... 

Biotin 515, 516,711, 721, 723 - 730,723s biosynthesis of 718, 745 in enzymes, table 724 mechanism of action 725 - 729 nutritional requirement 756 Biotin-binding proteins 728 Biotin carboxylase 724 Biotin carboxyl carrier protein 724 Biotin holoenzyme synthetase 724... 

Howard, P.K., Shaw, J. and Otsuka, A.J. (1985) Nucleotide sequence of the birA gene encoding the biotin operon repressor and biotin holoenzyme synthetase functions of Escherichia coli. Gene 35, 321-331... 

Wilson, K.P., Shewchuk, L.M., Brennan, R.G., Otsuka, A.J. and Matthews, B.W. (1992) Escherichia coli biotin holoenzyme synthetase-i>i<9 repressor crystal structure delineates the biotin and DNA-binding domains, Proc. Natl. Acad. Sci. USA 89, 9257-9261... 

Biotin apotranscarboxylase synthetase catalyzes the formation of the 6-N-(+)-biotinyl-L-lysyl carbon-nitrogen bond in methylmalonyl CoA oxaloacetic transcarboxylase. The conversion of the apoenzyme into the holoenzyme requires biotin, ATP, and Mg. A (H-)-biotinyl-5 -AMP enzyme complex seems to be formed in the course of that reaction (see Fig. 4-14). 

Biotin functions to transfer carbon dioxide in a small number of carboxylation reactions. A holocarboxylase synthetase acts on a lysine residue of the apoenzymes of acetyl-CoA carboxylase, pymvate carboxylase, propi-onyl-CoA carboxylase, or methylcrotonyl-CoA carboxylase to react with free biotin to form the biocytin residue of the holoenzyme. The reactive intermediate is 1-7V-carboxybiocytin, formed from bicarbonate in an ATP-dependent reaction. The carboxyl group is then transferred to the substrate for carboxylation (Figure 21—1). 

In biotin-dependent enzymes the cofactor is covalently linked to the protein through an amide bound to a lysine residue (Fig. 7). The attachment of free biotin to apo-enzymes is catalyzed by holocarboxylase synthetases (HCS). This reaction occurs in two steps, an activation step yielding biotinyl-5 -AMP (Eq. 1), which then reacts in a second step with the lysine e-amino group of the apoenzyme, yielding the active holoenzyme (Eq. 2) ... 

---