Fig. 8
From: 13C tracer analysis suggests extensive recycling of endogenous CO2 in vivo
Proposed routes of CO2 incorporation into different metabolomic pathways. [4-13C]-Oxaloacetate produced from pyruvate carboxylation with 13CO2 is assumed to result in [1-13C] and [4-13C]-fumarate, since fumarate is a symmetrical molecule and malate dehydrogenase and fumarase catalyze reversible reactions. Red and pink balls represent 13C. Pink ball illustrates the carbon scrambling in fumarate