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. Author manuscript; available in PMC: 2013 Nov 1.
Published in final edited form as: Biochim Biophys Acta. 2011 Dec 8;1824(11):1264–1277. doi: 10.1016/j.bbapap.2011.11.008

Figure 3.

Figure 3

Using d3-SP TpT as the enzyme substrate to illustrate the expected reaction products according to the current SPL mechanism shown in Scheme 3. (A): The 5′-dA radical abstracts the protium at the H6proR position to initiate the reaction. All three deuterium atoms in compound 2 should be retained in the repair product TpT; thus d3-TpT as well as regular 5′-dA and SAM are expected after the reaction. (B): The 5′-dA radical abstracts the deuterium at the H6proS position to initiate the reaction. Correspondingly, a deuterium is incorporated into the resulting 5′-dA and d2/d3-TpT and d1/d0-SAM mixtures are expected by the end of the reaction due to the H or D abstraction from the methyl group of 5′-dA by the TpT radical in the H atom back donation step.