Nothing Special   »   [go: up one dir, main page]
Scribd Logo
Upload

Welcome to Scribd!

  • 72 views

    Lesson 4.2. Glycoconjugates

    Uploaded by

    Gemma Cabañas
    This document discusses glycoconjugates, which are carbohydrates covalently bonded to other biomolecules like proteins and lipids. It describes two main types of glycoconjugates: glycolipids, which combine carbohydrates and lipids, and glycoproteins, which combine carbohydrates and proteins. Glycoproteins serve many important biological functions, such as structure, transport, and acting as receptors. One example discussed is syndecan, a glycoprotein involved in preventing blood clots through interactions between its carbohydrate chains, antithrombin, thrombin, and other clotting factors.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    Lesson 4.2. Glycoconjugates

    Uploaded by

    Gemma Cabañas
    72 views4 pages
    This document discusses glycoconjugates, which are carbohydrates covalently bonded to other biomolecules like proteins and lipids. It describes two main types of glycoconjugates: glycolipids, which combine carbohydrates and lipids, and glycoproteins, which combine carbohydrates and proteins. Glycoproteins serve many important biological functions, such as structure, transport, and acting as receptors. One example discussed is syndecan, a glycoprotein involved in preventing blood clots through interactions between its carbohydrate chains, antithrombin, thrombin, and other clotting factors.

    Original Description:

    Copyright

    © © All Rights Reserved

    Available Formats

    PDF, TXT or read online from Scribd

    Did you find this document useful?

    Is this content inappropriate?

    This document discusses glycoconjugates, which are carbohydrates covalently bonded to other biomolecules like proteins and lipids. It describes two main types of glycoconjugates: glycolipids, which combine carbohydrates and lipids, and glycoproteins, which combine carbohydrates and proteins. Glycoproteins serve many important biological functions, such as structure, transport, and acting as receptors. One example discussed is syndecan, a glycoprotein involved in preventing blood clots through interactions between its carbohydrate chains, antithrombin, thrombin, and other clotting factors.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    72 views4 pages

    Lesson 4.2. Glycoconjugates

    Uploaded by

    Gemma Cabañas
    This document discusses glycoconjugates, which are carbohydrates covalently bonded to other biomolecules like proteins and lipids. It describes two main types of glycoconjugates: glycolipids, which combine carbohydrates and lipids, and glycoproteins, which combine carbohydrates and proteins. Glycoproteins serve many important biological functions, such as structure, transport, and acting as receptors. One example discussed is syndecan, a glycoprotein involved in preventing blood clots through interactions between its carbohydrate chains, antithrombin, thrombin, and other clotting factors.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 4

    Lesson 4.

    2: Glycoconjugates
    Lesson Summary
    This lesson will discuss the different association of carbohydrates with other non-carbohydrate
    molecules. This will also discuss the importance and functions of glycoconjugates.

    Learning Outcomes
    At the end of this lesson, the student should be able to:

    1. Identify the different types of glycoconjugates, and

    2. Discuss the occurrence, importance and functions of glycoconjugates.

    Motivation Question
    What are other molecules attached to carbohydrates?

    Discussion
    Glycoconjugates

    Glycoconjugate is a molecule of carbohydrates covalently bonded with other biomolecules such


    as proteins and lipids. Most of the carbohydrates in glycoconjugates are oligosaccharides. The
    oligosaccharides in glycoconjugates may serve a structural function, for reactivity and surface
    recognition. As a hydrophilic molecule oligosaccharide has a good structural function for protein
    surfaces. In terms of reactivity, oligosaccharides may shield the surface and thus affect
    reactivity. Also, oligosaccharides may serve as label such as in label proteins and also serves
    as intracellular communication.

    Glycolipids

    Glycolipids are glycoconjugates of carbohydrates and lipids and is common among membrane
    lipids.

    The lipids are generally hydrophobic (water fearing) and the oligosaccharides are hydrophilic.
    Glycolipids generally serve as a surface recognition site.
    Figure 55. Structure of glycolipids

    Glycoproteins

    Glycoproteins are glycoconjugate of proteins and carbohydrates and has a wide variable
    composition (microheterogeneity). It also has a large array of functions such as for structure,
    transport, enzymes, receptors, etc. The carbohydrate chains are often short (oligosaccharides),
    though not all, and may be branched. The carbohydrate moiety is synthesized by enzymatic
    reaction and covalently linked to polypeptide (protein component).

    Examples of glycoprotein are the proteoglycans and peptidoglycan. Proteoglycans are


    extracellular aggregate of protein and glycosaminoglycans. It has a core protein where the
    carbohydrate unit will form a glycosidic bound to the oxygen of the serine or threonine amino
    acids in the core protein. Proteoglycan aggregates also has a single hyaluronoate molecule
    backbone.

    Peptidoglycan is a glycoprotein of covalently linked polysaccharide and polypeptide chain and is


    common among bacterial cell wall. With these linking, the amino acids in the protein component
    can resist hydrolysis by peptidases making it invulnerable by degrading enzymes. However, this
    can be broken down by the lysozyme. Peptidoglycan made certain bacteria resistant to several
    harmful factors. Penicillin was proven to inhibit the cross-linking of the polysaccharides and
    polypeptides, or the synthesis of the peptidoglycan. However, through time, Bacteria developed
    a resistance with penicillin.

    Glycoproteins serve several biological importance aside from its structural functions. It also acts
    as surface recognition, specifically the carbohydrate component, such as the syndecan.
    Syndecan are human membrane core protein with heparan sulfate carbohydrate units.
    Figure 56. Glycoproteins embedded in the plasma membrane

    This glycoprotein plays a very important role in the prevention of blood clot. The carbohydrate
    unit in this glycoprotein has a sulfated monosaccharide chain (NS domain) which is serves as
    binding site for the antithrombin (AT) molecule.

    Figure 57. The sulfated domain in the oligosaccharide of heparan sulfate

    Figure 58. The binding of AT to the S domain lading to the conformational change for factor Xa to attach

    In the presence of the sulfated monosaccharide chain in the glycoprotein, the protein
    antithrombin will attached causing it to have a conformational change in its structure. This
    conformational change of the antithrombin will allow its interaction with Factor Xa, a blood
    clotting factor. Without the conformational change of AT, due to its binding to the sulfated
    carbohydrate moiety in syndecan, factor Xa cannot bind to AT thus uncontrolled bleeding may
    occur.
    On the other hand, if thrombin and antithrombin molecules are present, it will bind to two
    adjacent NS domains in the heparan sulfate bringing the two proteins in closer proximity which
    will lead to its interaction. The attached thrombin to the AT will inhibit the interaction of factor Xa.
    In this case blood clotting will be inhibited.

    Figure 59. Interaction of thrombin to antithrombin inhibiting the attachment of factor Xa

    You might also like