Pentose Phosphate Pathway Hexose Monophosphate Pathway Metabolism Pentose phosphate pathway: phases, reactions, & metabolic roles Explain how Inactivity or absence of Glucose 6 phosphate dehydrogenase ; a rate limiting enzyme in the Pentose phosphate pathway could lead to oxidative stress.* The pentose phosphate pathway (PPP) in neuronal energy metabolism. Download Scientific Diagram HMP also known as the Pentose phosphate pathway. Consists of two irreversible oxidative rxs followed by a series of reversible