School of Biosciences

Image of Tim Parr

Tim Parr

Associate Professor in Nutritional Biochemistry, Faculty of Science


  • workRoom B23 North Laboratory
    Sutton Bonington Campus
    Sutton Bonington
    LE12 5RD
  • work0115 951 6128
  • fax0115 951 6122

Research Summary

Skeletal Muscle Protein Turnover: regulation of proteolysis.

Although skeletal muscle has a primary function of providing locomotion, it is a major depository of protein and free amino acids which are used for gluconeogenesis, wound healing and synthesis of antibodies and acute phase proteins during catabolic diseases. Loss of lean body mass is associated with loss of strength, immune function and with increased disability and mortality. Muscle protein turnover, the balance between protein synthesis and protein breakdown, is effected by various physiological states such as fasting, feeding, disease and aging resulting in a net increase or decrease in protein deposition.

Our research is being carried out into the mechanisms controlling protein degradation, how nutrition modulates this process and how proteolysis by specific enzymes influences metabolism. Our studies have predominantly focused on role of proteolytic enzymes from the calpain family which are believed to be involved in the initiation of muscle protein turnover and have been linked to regulation of carbohydrate oxidation. We are involved in trying to determine the interrelationship between these enzymes and how their activity is regulated, both in the short- and long-term. Changes in these enzymes are being monitored at the gene level, using cDNA and genomic probes, and at the protein level using antibodies. Many of these molecular probes have been generated in-house.

Through the understanding the control of proteolysis tangible benefits could be achieved. In the livestock industry efficiencies in protein gain are constantly being sort and this could be achieved by decreased protein degradation. Also in catabolic conditions, such as in cachexia and sarcopenia, modulation of proteolysis could help to prevent detrimental wasting.

Meat Quality: the role of proteolytic enzyme systems.

The cleavage of specific proteins that maintain the structure of skeletal muscle by proteolytic enzymes is an important factor post-mortem which allows meat to tenderise. Variability in tenderisation process affects meat quality and this has economic consequences for the livestock industry.

The calpain proteolytic system consists of calpain enzyme isoforms and a specific endogenous inhibitor calpastatin. Variation in the ratio of enzyme to inhibitor has been correlated to differences in meat quality; greater toughness being associated with elevated calpastatin activity. We are investigating the role the calpain proteolytic system along with other potential "initiating" proteolytic enzyme systems in the process of meat.

Selected Publications

School of Biosciences

University of Nottingham
Sutton Bonington Campus
Nr Loughborough
LE12 5RD, UK

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