Anaplerotic reactions

Overview
Anaplerotic reactions are those that form intermediates of the TCA or citric acid cycle. The malate is created by PEP carboxylase and malate dehydrogenase in the cytosol. Malate, in the mitochondrial matrix, can be used to make pyruvate (catalyzed by NAD+ malic enzyme) or oxaloacetic acid, both of which can enter the citric acid cycle. As this is a cycle, formation of any of the intermediates can be used to 'top up' the whole cycle. Anaplerotic is of Greek origin, meaning "to fill up".

There are 4 reactions classed as anaplerotic, although the production of oxaloacetate from pyruvate is probably the most important physiologically.