Glyteine (gamma-glutamylcysteine) is the immediate precursor to glutathione. During ageing and in many chronic conditions, cells in our body lose the capacity to make enough Glyteine to maintain sufficient levels of cellular glutathione to fight off oxidative stress. Glyteine synthesis inside every cell is catalysed by glutamate cysteine ligase (GCL), and it is the unhealthy and permanent changes to this enzyme that result in insufficient Glyteine being produced.
Oral and injected glutathione supplements cannot overcome this deficiency within cells. Once entered into the blood stream, glutathione by itself cannot enter cells. It must be first broken down into its three amino acid components, glutamate, cysteine and glycine (for more detailed information, check Can glutathione supplements increase cellular glutathione?).
The three amino acids released by the breakdown of glutathione outside the cell can be transported into cells. The glutamate and cysteine can then feed into the GCL enzyme, however, in many cases, the enzyme is not functioning optimally or is damaged in some way, so it cannot increase the amount of Glyteine available for glutathione synthesis.
On the other hand, Glyteine, given as an oral supplement, can enter cells intact and, once inside, is converted to glutathione by the second synthesis enzyme, glutathione synthase. This provides Glyteine with the capacity to increase cellular glutathione levels above homeostasis. This may provide some transient relief to oxidative stress that may help cells affected by a damaged GCL recover and regain their healthy physiological function.