Figure 1

Regulation of the de novo purine biosynthetic pathway in B. subtilis. (A) Transcription regulation of pur operon by PurR and a guanine-sensing riboswitch. The pur operon repressor PurR is the main regulator of pur operon. PRPP antagonizes DNA binding of PurR, whereas abundant adenine enhances the activity of PurR to repress the expression of pur operon. The FMN riboswitch employs a mechanism for gene control that relies on the mutually exclusive formation of intrinsic transcription terminator and antiterminator stem structures. (B) Feedback inhibition regulation of purine pathway at metabolic levels. The black solid lines represent metabolic conversions, the dash-dotted lines depict enzyme activation, and the dotted lines depict feedback inhibition. Abbreviations: R5P, ribose-5-phosphate; PRPP, 5-phospho-α-D-ribosyl-1-pyrophosphate; PRA, 5-phospho-α-D-ribosylamin; IMP, inosine 5’-mono-phosphate; XMP, xanthosine 5’-mono-phosphate; GMP, guanosine 5’-mono-phosphate; GDP, guanosine 5’-di-phosphate; GTP, guanosine 5’-tri-phosphate; SAMP, succinyladenosine mono-phosphate; AMP, adenosine 5’-mono-phosphate; ADP, adenosine 5’-di-phosphate; ATP, adenosine 5’-tri-phosphate; prs, PRPP synthetase; purF, PRPP amidotransferases; purA, adenylosuccinate synthetase; purB, adenylosuccinate lyase; guaB, IMP dehydrogenase; guaA, GMP synthase; guaC, GMP reductase.