Vitamin E – Online Biochemistry Course Lecturio

vitamin E is the second of the fat soluble vitamins I'll talk about here vitamin e like vitamin K contains many compounds and there it would get categorized into two groups known as the takapa Rawls and the toko try tocotrienols within each group there are various stereo isomers that can occur this includes both sis trans isomers as well as isomers relating to the stereochemistry these molecules act like antioxidants and they do this by preventing the proliferation of reactive oxygen species as I will show vitamin E inhibits the production of reactive oxygen species by a chemical process not by an enzymatic process and this is a very important way that it functions vitamin E is the fat soluble vitamin equivalent of vitamin C which helps prevent the proliferation proliferation of reactive oxygen species in water soluble material an example tocopherol tocopheryl in an example tocotrienol is shown on the right now vitamin E is found most abundantly in wheat germ sunflowers and in safflower oils it acts counter to vitamin K in that it actually reduces the amount of clotting so a person who is on a coumadin or warfarin type medication we'll have to monitor how much vitamin E they're actually getting in their diet because they can actually be in danger of reducing clotting too significantly if they get too much vitamin E now vitamin E is really the vitamin about which we know the least and it's also the reason for that is it's very rarely ever deficient there are a few cases where it's known for deficiency but not very much the vitamin E therefore is little benefit to people to take supplements although a lot of people do take vitamin E supplements so there are some problems with overdose but it's not as severe as an overdose problem as one might have with vitamin A or our vitamin D for example so this figure shows the different forms of vitamin E that can exist among the both the teka Ferrell's and among the tocotrienols now and we see in the case of the tocopherols that in fact of all these molecules they differ primarily in the structure of the components attached at ring on the ring at positions r1 r2 and r3 so these varying structures give vitamin-e a variety of different forms we remember also that the isoprenes on the right side and the brackets are varying place for the numbers of units that are out there so we can imagine vitamin e molecules are quite varied and diverse in their structures there's the r1 the r2 and the r3 now that dotted line that you see within the isoprene unit is actually a varying point among the different tocopheryl versus the tryi nose that Mollett that that bond is a single bond in the takapa rolls which means that you wouldn't have a second line that's there or it's a double bond in the tocotrienols which means you would have a double bond er a second line there so we've compromised and put a dotted line to indicate that it could be either depending upon whether it's one form or the other now that the control is preferentially absorbed and stored in humans it prevents damage from reactive oxygen species as I've known as I've noted and it protects it the membrane lipids in particular we remember that the membrane has that very nonpolar portion of it and within that nonpolar portion is where toka alpha tocopherol and the vitamin E compounds will abundantly be found alpha tocopherol inhibits the lipid peroxidation chain reaction I'm going to show you that in a second but this is a repeated reaction that can generate a tremendous amount of lipid peroxides and lipid peroxides are very problematic within our body alpha tocopheryl inhibits protein kinase c which we've seen in another of the presentations and protein kinase c is involved in a signaling process and it also inhibits smooth muscle grows the growth as a result another thing that alpha tocopherol do is inhibit platelet stickiness and it's through this mechanism that the clotting tendency of the blood clotting process is reduced because the platelets sticking to each other is the very first step in the process of forming a clot it's known as the cellular response and stickiness is very critical for that process if vitamin K inhibits it it reduces the amount of clotting that can occur in the body so it's for this reason we don't want to take too much vitamin E and by the way I'm using the term alpha tocopheryl interchangeably with vitamin e because alpha tocopheryl turns out to be the most abundant form of vitamin E and also the most effective it's the one that's most easily absorbed within our intestines now vitamin E may have a role also in neurological function and the reason we think this is the case is that deficiency of vitamin E though it's not very common when it does occur it seems to lead to disorders among the the nervous system in this slide I want to describe the lipid peroxidation chain reaction that I described earlier now this reaction occurs along the fatty acid side chains of fatty acids in fats in the lipids of our membranes or in other places are found in the cell in this reaction there's our free radical molecules that are that are reacting with the lipids now we see on the top reaction first of all that there's a hydroxyl free radical that is interacting with the unsaturated lipid that unsaturated lipids change or altered in the process it loses water and creates moves the free radical from being on the hydroxyl group to being on the lipid itself so the fatty acid now is actually a free radical on its own free radicals can be very problematic for the cell because they proliferate very readily they're not stopped easily by enzymes and in fact enzymes would have a hard time keeping up with what these free radicals actually can do the free radical of the lipid can combine with molecular oxygen as you see here to form the lipid peroxidation on the right well we've now proliferated that into a new form which can then interact with yet another fatty acid and create yet another lipid radical so we see this sort of process occurring over over cyclically and cyclic processes like that can generate a tremendous amount of problem so what's important with vitamin E is vitamin E will actually prevent each of these free radicals from proliferating the molecules that I've described to you vitamin E chemically reacts with each one and stops it from being a free radical now that's a real value of an antioxidant vitamin C does a similar thing as I said for other components of the cell this prevention of the proliferation of the free radical stops this oxide process from occurring now that oxidative process that's occurring in the membranes of our cells is really really critical because it's involved in processes like atherosclerosis one of the steps in atherosclerosis involves oxidation of lipids being carried in our bloodstream by molecules called LDLs and when they react in the way that we've seen here the immune system attacks them and starts the formation of an atherosclerosis formation in the first place is a very critical feature so the free radicals with vitamin E are destroyed as I said the lipid peroxidation is completely halted vitamin E gets oxidized and now we think about well vitamin K had to be regenerated once it got oxidized vitamin E itself also has to be regenerated after it's been oxidized and it turns out the vitamin E is regenerated by reduction using vitamin C the other antioxidant vitamin vitamin a or a compound called ubiquinol any of those can help to regenerate vitamin E what we've seen vitamin C gets regenerated by the NADPH system so with all these things together the regenerative systems can make an essentially enough of the various vitamins that we need to have active at any given time