Escherichia coli (bacteria)
Coenzymes are small organic molecules that assist an enzyme during the catalysis of a reaction. Biotin, or Vitamin H, is one such coenzyme or cofactor in enzymatic carboxylation reactions in many organisms i.e. it helps the enzyme transfer a carboxylate group (-COO-) from one molecule to another. Though biotin is widely used in reactions, it cannot be synthesized in the human body and hence must be obtained through diet. The biotin biosynthesis pathway is the process of synthesizing biotin and is present only in plants and microorganisms. Hence it has been widely studied for the development of safe antimicrobial drugs and herbicides. Dethiobiotin synthetase (DBTS) functions in the third step of the biotin biosynthesis pathway. It catalyzes the ATP-dependent formation of dethiobiotin, from 7,8-diaminopelargonic acid and carbon dioxide.
The above structure is that of a single subunit of DBTS from E. coli. DBTS is a homodimer with each subunit consisting of a seven stranded parallel beta sheet flanked by helices on both sides. This fold is also seen in other phosphotransferases like adenylate kinase. Two equivalent active sites are located at the interface between the subunits in the DBTS homodimer. The loop Gly8-X-X-X-X-X-Gly14-Lys15-Thr16 is particularly important for the binding of ATP.
Protein Data Bank (PDB)
author: Ashwini Patil