Enzymes tailored to fit

PROTEIN engineers at the Institute of Food Research, Reading, in the UK have found the means to produce rugged and more efficient versions of a key enzyme -- phospholipase A2 or PLA2 -- used in the food and pharmaceutical industries.

PLA2 activates the breakdown of phospholipids, which are fat molecules found in the body, converting them into prostaglandins -- powerful biochemicals which dilate blood vessels, relax muscles and influence several physiologically important processes such as inflammation and blood clotting.

Synthetic prostaglandins have several therapeutic uses, and are manufactured using the enzyme phospholipase A2. They are used to control blood clotting and to induce labour in pregnant women. PLA2 is also used in the preparation of food emulsifiers -- reagents used for dissolving or suspending fatty foods in water. But like other enzymes, PLA2 is extremely sensitive to temperature and acidity.

Scientists have been trying to tailor this enzyme's properties to make it more stable, preventing it from being broken down at higher temperatures or at altered acidity levels, more active and selective in that it acts only on particular phospholipids, to make it suitable for diverse industrial applications.

The British team of scientists led by P W Goodenough targeted the gene that carries the instructions necessary for cells to normally produce PLA2. They altered the DNA sequence of the gene and then incorporated it into cultured cells.

One form of the modified enzyme produced by the altered gene, the scientists found was more stable but less active than its original form. However, another set of mutants showed a considerable increase in activity, but the stability of the enzyme remained largely unchanged.

Says M K Bhat, a member of Goodenough's team who presented this work at the International Congress on Biochemistry and Molecular Biology recently held in New Delhi, "Our ultimate aim is to produce an enzyme altered in such a way that it offers the maximum stability and is the most active -- which is the need of the pharmaceutical and food industries."