BIOTIN BIOSYNTHETIC ENZYMES AND THE METABOLIC CONTROL OF BIOTIN BIOSYNTHESIS

Jennifer A. Gray and Basil J. Nikolau

Biotin is a vital cofactor for many enzymes that facilitate carboxylation, decarboxylation, and transcarboxylation reactions. The biotin biosynthetic network has been well characterized in many microorganisms including E.coli (Eisenberg, 1973), but only recently have the genetic and biochemical components of the Arabidopsis biotin biosynthetic enzymes been discovered. Previous studies (Muralla et al. 2008) describe a chimeric gene locus (BIO3/BIO1) in Arabidopsis that can produce a transcript (BIO3/BIO1 (-10)) encoding dual catalytic activities, that of DAPA aminotransferase and dethiobiotin synthetase. Moreover, this locus could also produce a transcript (BIO3/BIO1 (+10)) that encodes only the penultimate reaction of the pathway, that of dethiobiotin synthetase. This study details the approach taken to identify and further isolate a putative BIO1 protein in Arabidopsis. In addition, the metabolic control that the AtBioF (BIO4), BIO2, bifunctional BIO3/BIO1 (-10), BIO3/BIO1 (+10) and the putative BIO1 proteins have on biotin yield was experimentally assessed. Observations support the hypothesis that DAPA aminotransferase activity is encoded by the bifunctional BIO3/BIO1 locus, and that the reaction is not catalyzed by a monofunctional BIO1 protein. Further analysis must be undertaken to divulge the details of the metabolic control on biotin production.