11/10/2022 0 Comments Ginger brave cursed face![]() ![]() In humans, elevated cysteine levels are associated with rheumatoid arthritis, Parkinson's and Alzheimer's disease, cardiovascular disease, and systemic lupus erythematosus. Why would you need a pathway to get rid of cysteine? Well, just on general principles you'll often see pathways that balance the synthesis and breakdown of compounds in the body, but also there is some evidence that excess cysteine contributes to some diseases: In birds, there is clear physiological evidence that excess cysteine levels contributes to metabolic acidosis, thinning of egg shells, and growth inhibition. That last hypothesis is interesting because it fits with a couple of observations, and also makes some predictions. ![]() Gillian Anderson and Ewan McGregor are good-looking people their coloring helps distinguish them from others.Īnd here's another new idea: the pheomelanin pathway exists as a sink for excess cysteine. Similarly, there's nothing sexually unattractive about red hair in humans, and many people find it extremely attractive. In birds in particular, pheomelanin is used as a marker for sex you can't get rid of it without losing bright, bold signals that males use to advertise their availability. Pheomelanin is all over the place among the vertebrates, though, so I suspect this isn't the case it seems to have some utility. Red hair is not a serious detriment to survival it could simply be that it persists as a part of a biochemical pathway that isn't easily blocked, or that it's disadvantages aren't great enough to have led to its removal over time. I can give you a couple of hypothetical reasons, though.ĭon't assume that because a trait is deleterious it must be culled by natural selection. You see the problem: WHY DO GINGERS EVEN EXIST? It just seems to be a bad thing all around. More pheomelanic birds are also more sensitive to environmental stress - they're more fragile. Just to add further insult, studies in birds have found evidence of a physiological trade-off: increased pheomelanogenesis (that is, birds with more red plumage) is correlated with reduced brain size. If cysteine incorporated into the pheomelanogenesis pathway comes from an excess pool, then pheomelanogenesis could represent an excretory mechanism of cysteine and an adaptive process that may explain the evolution of pheomelanin. Cysteine also reacts with dopaquinone thus participat- ing in the synthesis of pheomelanin that takes place in melanosomes. In birds, excess dietary amino acids are also diverted to the synthesis of uric acid, the main product of excretion in birds. This excess, which can be toxic, is partly eliminated by cysteine sulfoxidation, a process mainly catalyzed by cysteine dioxygenase (CDO) in which less toxic products than cysteine such as sulfate and taurine are formed. When the levels of cysteine are higher than required for these functions, especially for protein synthesis, excess cysteine occurs. It is also used for the synthesis of reduced glutathione (GSH), which is the main storage of cysteine and thus also acts as a source of cysteine. This amino acid is used for protein synthesis, and can be recovered by protein breakdown. So making red hair actually depletes the body of a protective substance, and has the side-effect of producing carcinogens.Ĭhart showing the physiological activity of dietary cysteine. It's also synthesized biochemically by a process that consumes glutathione (GSH), an important cellular anti-oxidant. In fact, pheomelanin is prone to photodamage (exposure to light causes it to break down) that produces carcinogenic byproducts. Ginger brave cursed face full#Red hair is stuffed full of pheomelanin rather than eumelanin.īut here's the thing: pheomelanin is a lousy barrier to UV. We all make it to varying degrees - nipples and lips get their reddish color from it - but some people make it in much larger quantities than they do eumelanin. If you're dark-haired, it's because the keratinocytes are stuffed full of eumelanin, which is also an excellent barrier to UV damage. ![]() We vertebrates produce primarily two forms of melanin, eumelanin and pheomelanin.Įumelanin is a dark pigment cells loaded up with it look black or dark gray. Pigmentation is produced by the deposition of a complex light absorptive polymer called melanin in cells. The biochemical cause of these differences are known. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |