Manufacture of the industrial enzyme gamma glutamyl transpeptidase (GGT) from bovine kidney

Summary

Background
Gamma-Glutamyl Cysteine (GGC) is the immediate natural precursor to the master antioxidant glutathione. A key step in the GGC manufacturing process is the use of the enzyme GGT, the richest source being bovine kidneys.
The objective of the project was to develop pilot studies for the cost effective production of a crude GGT enzyme concentrate with the process being suitable for installation at an abattoir with minimal impact on its core meat processing operations.
Research
A key step in the GGC manufacturing process is the use of the enzyme, gamma glutamyl transpeptidase (GGT).  The richest natural source of this enzyme is bovine kidney.  Currently, the GGT enzyme is commercially available in low volume (mg) as a research reagent from various animal sources, bovine, porcine and equine.  Biospecialties Australia’s new GGC manufacturing process requires the use of GGT as an industrial enzyme and, as such, it must become available at large volume (tonnes) and at low cost.
The current pilot scale process for the manufacture of GGC requires approximately 2.8 kg of bovine kidney to supply sufficient enzyme to produce 1 kg of GGC in a batch process, where the enzyme is not immobilised and is not recycled.  For industrial scale, it would be preferable to immobilise the enzyme so that it can be recycled for use in subsequent reactions.  The use of immobilised enzyme not only offers the benefit of reduced manufacturing costs but also improved processing and GGC purification.  Immobilised enzymes can normally be recycled for between 10-50 reactions before the specific activity diminishes below a suitable threshold level for the manufacturing process.  The number of reactions possible with an immobilised enzyme is dependent on the reaction conditions, the stability and structure of the particular enzyme, and the nature of the immobilising matrix.  
At full industrial scale, it was envisaged that the production of the GGT enzyme would involve an abattoir based extraction, concentration and stabilisation of the GGT from harvested healthy kidneys.  Ideally, the subsequent processing technology to purify and immobilise the enzyme would also be suitable for operation by normal abattoir staff. If not, the crude extract could be shipped and sold to BSA, which would conduct the final processing steps.   
Outcomes
The process development for the production of the enzyme γ-glutamyltranspeptidase was completed. However, there was no comemrcial takeup of this technology by processors.