Pyridoxine B6 common reactions and not just one before the test We are skipping to this one because she wanted to get Folate and Cobalamin in because of Sources of animal products such as beef salmon and light meat chicken We also can get it form Supplements include pyridoxine hydrochloride Naturally occurring sources are always going to whole grain products bananas and nuts be the best bioavailable B6 is lost through heating canning milling freezing and sterilization It doesn t mean cooking meat rids all of the B6 you will still be getting good amount But if you have something that isn t very bioavailable and doesn t contain much B6 and it then goes through milling well then you will get destroying of B6 Freezing a banana which has a little B6 would rid pretty much any B6 it had PN PL and PM are your vitamins When we phosphorylate them they turn into the coenzymes PNP PLP and PMP Remember vitamins are the smaller form for transportation The most commonly used one is PLP Absorption It is eaten in all 6 forms stated above In the intestine at the brush border our phosphorylated forms become dephosphorylated so your coenzymes go back to your vitamin form PNP PLP PMP PN PL PM In the jejunum we have passive diffusion not dose dependent like we have seen in other vitamins and absorb 75 of B6 that we consumed Once it enters the enterocyte it can be used or it can enter the portal bloodstream and then to the liver and other tissues In the tissues She stated that B vitamins are not stored but B6 and B12 are exceptions B6 is referred to more as a reservoir rather than storage In the liver we store 5 10 of vitamin This is also the site of vitamin metabolism where the vitamin goes to co PN PNP PLP PM PMP PLP PL PLP enzyme forms Eventually almost all will turn into PLP which again is the most used form The solid black arrow is using the enzyme kinase which uses ATP but the red arrow uses PMP or PNP oxidase which utilizes riboflavin FMN This ties riboflavin and B6 together by the use of FMN to form PLP In the muscle is where we get the big uses or stores of the vitamin It stores 75 85 of vitamin Stored PLP is tied to glycogen phosphorylase and that is why it is delivered to muscle This makes it more stable and unable to diffuse from the cell B6 is used in a lot of reactions especially the ones involving A A So if you see B6 think A A Remember that A A have a few main ways to metabolize transamination deamination Decarboxylation and side chain cleavage Remember that transamination is the formation of nonessential A A It is when you take one amine group off of an A A and you place it on an keto skeleton to make another A A which is non essential extra slide She just showed some transamination reactions such as https www google com search q transamination source lnms tbm isch sa X ei dD UUee1MoXC0AGNmoHYCQ ved 0CAcQ AUoAQ biw 1366 bih 643 facrc imgdii imgrc XGFCAMTuDcrWRM 3A 3BBji AKaOTLxTCM 3Bhttp 253A 252F 252Fthemedicalbiochemistrypage org 252Fimages 252Faminotransferasereaction jpg 3Bhttp 253A 252F 252Fthemedicalbiochemistrypage org 252Fnitrogen metabolism php 3B561 3B186 Here we see Alanine going to pyruvate using PLP and ALT to form ketoacid and A A form ketoacid and A A can use PLP and AST to form Aspartate and Oxaloacetate The AST and ALT enzymes used for liver tests Decarboxylation is used to form NT synthesis We will go from Glutamate GABA NT inhibitor and from L dopa dopamine Dopa is made from Tyrosine All of these use B6 Side chained cleavage is one of the least used methods for metabolism of A A We see Serine Glycine It cleaves hydroxymethyl group off of methyl tetrahydrofolate MTHF and attaches to serine to form Glycine the enzyme used is serine hydroxyl methyltransferase which requires PLP Deamination occurs in the liver for the urea cycle and in the kidneys to create NH4 and maintain pH balance of Threonine ammonium PLP Then we reaction in Transulfydration Methionine Homocysteine Cystathionine Cysteine using Cystathionine Synthase and Lyase which require PLP Homocysteine is a risk factor for heart disease We don t want Homocysteine because high levels are risk factor for Coronary heart disease inflammation and other problems with the heart So we need B6 to break it down Cysteine can be formed into Taurine which we will talk about later For example if we take amine group off we would get an ketoacid and which would be excreted That requires have the Methionine Cysteine We also need B6 for synthesis of Porphyrins Porphyrin ring is the ring that is heme PLP coenzyme is used for aminolevulinic acid synthase ALA So Succinyl CoA Lysine uses PLP to make a bunch of intermediates to ultimately form heme We form heme to be able to carry Fe throughout the blood Heme is 4 protein Fe subunits so you get 1 heme per subunit So basically B6 is necessary for heme production Without B6 you won t be able to make heme which means you won t be able to carry oxygen or iron which could cause Anemia Not having PLP can cause anemia but is also used for synthesis of Niacin from Tryptophan Without B6 it will be a Niacin deficiency and instead your Tryptophan will form Xanthurenic Acid Is excreted then in the urine So one way to test for B6 deficiency is to give Tryptophan and find out if you have this acid in the urine B6 is also in the formation of Carnitine which we saw was needed to bring fatty acid into the mitochondria for Beta oxidation and then through the Krebs cycle We see it in eicosanoids when Linoleic acid goes to Arachadonic acid Lastly we see it in glycogen to glucose 6 phosphate using glycogen Phosphorylase This is important because most of our B6 is in the liver and the muscle as stated before Assessment can be done by urine You can look at excreted 4 pyridoxic acid which is riboflavin dependent Urinary assessments are indicative of intake not stores Another assessment is RBC amino transferase activities because transferases are used in transamination reactions Plasma PLP or the coenzyme forms and there are also indirect tests These indirect tests include Tryptophan and or Methionine load test For Tryptophan you can look at how much Niacin or Xanthurenic acid you get For Methionine you will look at urinary cystathionine because without B6 you wouldn t see this but rather Homocysteine Deficiency Are rare and was a problem in the 1950s with infant formula Some symptoms are dermatitis on face neck shoulders and butt along with weakness and being fatigued Cheilosis glossitis and angular
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