glutamyl transpeptidase glutathione Scheme of γ-glutamyl cycle, the synthesis of GSH according particular Glutamyl)peptide The Role of Glutathione Metabolism

If I understand rightly you haven't an absorption problem.So once on supplements or a richer B12 diet you can store and utilise b12 from your liver

Researchers have expressed roGFP2-Grx1 in the cytosol, mitochondrial matrix, endoplasmic reticulum, and nucleus to map compartmentalized glutathione redox dynamics

Supplementing with liposomal glutathione may support liver function, healthy aging, exercise recovery, and immune responseespecially under high oxidative stress

Therefore, intracellular esterase activity was calculated as mean fluorescence intensity of sample normalized to mean fluorescence intensity of control one