MCB 450 1st Edition Lecture 7 Outline of Last Lecture I Monosaccharides II Glycosidic bonds III Polysaccharides Outline of Current Lecture I Some Explanations a Glycoconjugates b Proteoglycans c Glycoproteins d Glycan Synthesis II Examples of Importance of Glycans Current Lecture Asparagine linked N glycoproteins Biosynthetic pathway is very highly conserved in eukaryotes Oligosaccharide is built up on and transferred from a carrier lipid Lumen interior of endoplasmic reticulum 7 14 slide missing diagram N linked saccharides are trimmed further and new sugars are added back in the Golgi Golgi is the compartment that follows the endoplasmic reticulum N linked glycans are important If an asparagine is missing it leads to congenital defects Mucins are heavily O glycosylated Mucins long proteins that are very rich in serines and threonines the hair like projections are short O linked chains o Makes a rather stiff molecule o Very hydrated o Very similar concept to the glycosaminoglycans o Coats various mucus membranes forms a gel like substance Contribution of carbohydrate to protein structure If you took two sugars and expected them to automatically make a bond in a solution that wouldn t happen the reaction is energetically unfavorable Energetics of glycosidic bond formation UDP glucose nucleotide Universal donors used in all factions of life These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Nucleophiles and leaving groups Activation by UDP is what makes it want to accept a reaction with a nucleophile Cellulose most abundant polymer on the planet Glycosyltransferases can have inverting or retaining mechanisms Exam questions expect to know that donor has an alpha linked linkage Inverting or retaining mechanism Glycogen synthase Retaining Cellulose synthase Inverted Carbohydrate protein interactions Antibodies will recognize certain types of carbohydrates Lectins Lectins do not come from immune system o Can distinguish between subtle differences in carbohydrate structures o Toxin will be attracted to the lectin that is present on a glycoprotein wall Purple diamonds sialic acid Hemagglutinin binds to sialic acids then will make it across the cell wall to infect the cell Different subtypes of influenza are described by their different types of hemagglutinin and neuraminidase o Ex H1N1 Different Hs and Ns define influenza virus A subtypes o H1N1 Spanish flu o H3N2 1968 Hong Kong flu o H5N1 Bird flu The castor bean toxin ricin has a lectin domain Why you should not eat raw castor beans o Compound is extremely distructive o Bulgarian journalist was injected with ricin by an umbrella contraption in the 60s ABO H blood group antigens Straightforward genetic basis for blood type in humans Type O mutation where it eliminates the transferase altogether Erythropoietin Illustrates the importance of human physiology EPO is a hormone and is normally produced in the kidney o Where our body notices lower than normal levels of oxygen and then will secrete EPO into the blood stream o Stimulates red blood cell production EPO improves performance in endurance sports o Increases oxygen supply to muscles o Used in long distance bicycle races