The global production of enzyme reached more than $US 1.8 billion per annum. Although contribution of plant biotechnology in enzyme production is meagre but there is every potential to increase in large scale.
The first commercially produced enzymes in plants are avidin and β-glucoronidase. They were produced in transgenic maize. Following success, production of several of these industrially important enzymes was attempted.
Some of the industrially, important enzymes such as cellulase and xylanase, which have been produced in plants. Interestingly these enzymes normally targeted against component of cell wall. These are generally produced in micrograms using conventional fermentation technology. These are a considerable demand for the enzymes from paper textile industries for the production of bioethanol, etc.
However, there are apprehensions that expression of this enzyme in plants may leads to the risk of autodigestion. But modified thermostable forms of the enzyme were produced in transgenic plants without giving chance for auto-digestion.
Their activity has been completely checked in the transgenic plants at which plants normally grow. Their optimum activity could be seen only after their extraction from plant and heated to higher temperature.
Another enzyme produced in transgenic plants was phytase, used to hydrolyse inositol hexaphosphate (phytate) to sugar alcohol inositol and inorganic phosphate. Phytate is the substrate for the enzyme phytase found in large quantities in seed used as animal feed. Phytase releases phosphate from substrate that is normally indigestable to monogastric animal.
As phytate is present in seed and used as animal feed they do not get benefit from the source of phosphate. As a consequence, indigestable phytate from animals are releases through faecal matter and build up their concentration in environment.
Transgenic plants expressing phytase into seed can be given as animal feed. Phosphate utilization is increased due to the presence of phytase enzyme and phosphate excretion is decreased.