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. Author manuscript; available in PMC: 2014 May 15.
Published in final edited form as: Bioorg Chem. 2012 Jan 31;43:15–25. doi: 10.1016/j.bioorg.2012.01.001

Figure 4.

Figure 4

Biosynthesis of preQ0. Biosynthesis of 7-cyano-7-deazaguanine core of deazapurines from GTP is accomplished by the successive actions of GTP cyclohydrolase I (GCH I/ToyD), CPH4 synthase (QueD/ToyB), CDG synthase (QueE/ToyC) and preQ0 synthetase (QueC/ToyM). The loss of 3 carbon atoms by the successive actions of GCH I and QueD, elimination of a nitrogen by QueE and incorporation of ammonia by QueC have been demonstrated by high resolution mass spectrometry [56,62]. Loss of the nitrogen as ammonia from CPH4 catalyzed by QueE has not been demonstrated explicitly.