My teacher taught me in a lecture that PEP forms from Pyruvate by two ways, based on their sources, that is - 1. If the Pyruvate was from lactate (by lactate dehydrogenase action), it gets shuttled into mitochondria and is successively converted to OAA and PEP, by enzymes PC and PEPCK(mitochondrial) respectively. This PEP is then shuttled to cytosol for rest of gluconeogenic steps to take place. 2. Whereas, if the Pyruvate was from any other source, it is shuttled to the mitochondria, where it is converted to OAA by PC. It is then shuttled to cytosol by malate shuttle and then converted to PEP by PEPCK (cytosolic). Why the difference in mechanism? Please correct me if any of these steps are wrong.