Gluconeogenesis Pentose Phosphate Pathway HMP also known as the Pentose phosphate pathway. Consists of two irreversible oxidative rxs followed by a series of reversible 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 return of metabolism: biochemistry and physiology of the pentose phosphate pathway Stincone 2015 Biological Reviews Wiley Online Library