There appears to be overwhelming evidence that (MS) is in fact a cuproenzyme, leaving me kind of scratching my head at its exclusion or antagonism in any methylation programs, specifically those involving B12/Folate. Keep in mind that a long standing copper deficiency results in copper toxicity by nature of coppers role in the body. Blood tests are inconclusive on this matter as high copper in blood serum can be an indicator of any level of inflammation, infection or oxidative stress in the body. A liver biopsy is the only reliable method of determining copper status in the body. https://www.ncbi.nlm.nih.gov/pubmed/10350650 Copper deficient rats saw a 21% reduction in (MS) activity. Copper deficient rats saw elevated hepatic 5-methyltetrahydrofolate and homocysteine concentrations. https://www.ncbi.nlm.nih.gov/pubmed/17513393 Copper deficient rats saw a significant decrease in plasma homocysteine. Copper deficient rats saw down regulation in BHMT function (MS shortcut). Trimethylglycine (Betaine) lowers homocysteine substantially. Copper deficient rats saw increased amounts of gluathione. This is in contrast to longstanding copper deficiency which eventually leads to increased homocysteine. Shortterm loss of homocysteine through the transulfuration will lead to longterm (MS) dysfunction. https://www.ncbi.nlm.nih.gov/pubmed/18472229 Copper deficient myleopathy is strikingly similar to subacute combined degeneration (SCD) of which B12 is involved. http://m.pnas.org/content/101/12/4234.full There is indication in a rare case of s-adenosyl-homocysteine hydroylase deficiency that copper dysregulation exists between homocysteine to methinionine, and not pre-homocysteine. Ceruloplasmin and copper levels were found to be normal in the case of 30 and 150x fold increases to AdoMet and AdoHcy respectively. A lowered demand for homocysteine recycling appears to spare copper. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0076209 Homocysteine directly antagonizes serum copper levels, preventing the healthy functioning of cuproenzymes. Copper, as it appears to be essential to the functioning of methinione synthase, could in a time of infection or stress, be spread far too thin in the body to adequately break down homocysteine, leading to an eventual antagonism of copper, creating a deficiency state alongside a toxic state. Inadequate copper supply will hinder the (MS) enzyme, preventing the breakdown of homocysteine, further increasing the need for copper to break down homocysteine, further impairing cuproenzyme activity until eventually (MS) has lost function creating an exponentially worsened state of copper deficiency in the body. Ceruloplasmin is copper dependant and is required to remove copper from the body (histidine seems to serve this same function very well), in cases where ceruloplasmin is impaired, copper will build up in tissues. Increasing the demand for Zinc to create (MT), impairing zinc functions throughout the body, eventually lowering CuZnSOD and causing extreme oxidative stress throughout the body, depleting essential minerals everywhere through a cascading effect. In a histidine deficient state, our secondary carrier and eliminator of copper from the body is also impaired, thus a copper and histidine deficient state over a period of time eventually guarantees high oxidative stress, impaired copper function, copper deficiency and toxic levels of copper in the body, impaired zinc function, and overall incredibly impaired methylation cycle. Lacking Histidine (powerful metal carrier) SOD, MT and Cp will allow heavy metals to run rampant the body, leading to increased accumulation. These metals also antagonize copper and zinc. It seems to me that if a person has been on a methylation protocol for several months and isn't getting better they should consider what methinionine synthase is fundamentally. Supplementing or refeeding copper will not correct this deficiency and is incredibly dangerous, as it will reactivate many enzymatic functions that have been shut down or slowed down over time, resulting in an even higher need for copper without any adequate way of removing it afterwards. I'm doing research on carnosine, that's in the general forum if you'd like to these a look, but I've been curious about it in regards to methylation for a while and figured I'd do a quick bit of research on it in regards to methylation. My current idea for rebalancing copper and zinc in the body is through the use of Carnosine (histidine is absolutely required for all essential mineral functioning and transportation in the body, including MT, SOD and ceruloplasmin, as well as the chelation of free copper from the body), a balanced diet including copper at adequate levels, TMG at dosages ranging from 3-12 grams per day to temporarily offset the need of copper in (MS) when TMG can do a good enough job meanwhile, and obviously plenty of water and rest. I don't believe driving (MS) with folate and b12 is safe in as copper deficient state, though I'm not giving treatment advice here, just outlining my current research.