Structural and functional modifications of muscle proteins in response to glucosamine glycation

  • Author / Creator
    Hrynets, Yuliya
  • High quality proteins can be isolated from meat processing by-products. The main quality attributes of these isolates are measured through their essential amino acid composition and functional properties, such as solubility, water holding and emulsification capacities, and gelation. The isoelectric solubilization and precipitation process (ISP) is a technology that can recover and valorize muscle proteins from these low value raw materials. This process involves acid and alkaline solubilization followed by precipitation of the proteins at their isoelectric point. Despite ISP provides a good protein recovery yield, solubility with this technique is a major problem due to partial denaturation as a consequence of the extreme acid/alkaline conditions applied. Protein-saccharide interactions through Maillard reaction (glycation) is a promising solution to solve this issue, since can produce novel glycoproteins with enhanced functionality (i.e. solubility). Hence, one of the main objectives of this thesis was to study the interaction between myofibrillar protein and reducing sugars using two different approaches: 1) a chemical glycation conducted at low temperatures (40°C) in a liquid environment and 2) an enzymatic glycosylation involving transglutaminase (TGase) as a catalyst conducted at 37°C. Glucosamine (GlcN), a popular amino sugar used to treat osteoarthritis, was chosen as a glycating agent due to its unique chemical characteristics. It is a fast glycating agent and could be used by TGase as an acyl acceptor to form an isopeptide bond between the glutamine in the myofibrillar protein and the free -NH2 of a GlcN molecule. In the first part of the thesis, two studies were conducted. The first aimed to conjugate isolated actomyosin protein with glucosamine at 40°C in a liquid environment. Conjugation at 40°C for 8 h at a 1:3 protein:sugar ratio produced glycated myofibirillar proteins with enhanced solubility and emulsifying properties, particularly at the isoelectric point. In the second study, enzymatic glycosylation using TGase created a more stable glycosylated myofibrillar protein at 25 and 37°C, possibly due to the formation of an isopeptide bond between glutamine and GlcN. It was possible to obtain stable glycoconjugates at these lower temperatures which also possessed increased solubility and emulsifying properties. The 2nd part of the thesis was dedicated to understanding the unique chemistry of GlcN in vitro and how this would affect the structure of myoglobin, a major important globular protein found in muscle tissue. Two studies were conducted. The first focused to identify and quantify the main products of GlcN degradation at 37°C. GlcN produced a significant amount of α-dicarbonyl compounds (1000-6000 mg/kg of GlcN), particularly 3-deoxyglucosone and glucosone. GlcN cyclocondensation products, fructosazines and dihydrofructosazines, were also identified. The second study focused on the major structural changes of myoglobin in response to GlcN reactivity and degradation products. GlcN treatment may induce the production of fibrous aggregate in a relatively short time, while no such effect was observed for myoglobin glycated with glucose and acetyl-glucosamine. Overall, this thesis demonstrated that GlcN is a unique amino saccharide with the potential to be used in food applications (i.e. protein modification for improved solubility), and not only as a natural health product to treat osteoarthritis. However, further studies are necessary to evaluate the safety of GlcN as a food ingredient.

  • Subjects / Keywords
  • Graduation date
    Fall 2015
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.