The effect of builders on the activity of protease enzymes

The effect of builders on the stability of protease enzyme activity was studied in an effort to identify superior builders which are soluble in water and compatible with enzymes formulated into heavy duty laundry powders. Various poly(styrenesulfonate-methacrylate) copolymers, polyacrylate and tripolyphosphate anionic builders, as well as various poly(vinylalcohol-vinylacetate) nonionic copolymers, namely PVAs, were used. Zeolite 4A was also used as a typical nonphosphate particulate builder in the detergents. The protease used is frombacillus stearothermophilus. The calcium content was determined to be 16.7 mole/mole of protease by atomic spectrophotometry. In binary systems composed of a fixed concentration of 10 U/mL protease and varied concentrations of compound, builder or surfacant, it was found that compounds having the larger calcium ion binding capacity (C.B.C.) lowered the relative activity of protease enzyme. The activity of protease enzyme alone was lowered about 20% by addition of 0.02% sodium dodecylbenzene sulfonate (DBS). The anionic builders added to the binary system of fixed 10 U/mL protease and 0.02% DBS reduce the protease enzyme activity in proportion to the magnitude of their C.B.C. Addition of anionic builders further lowered the protease enzyme activity. The nonionic builders and the nonionic surfactant can enhance the protease enzyme activity by protection of protease against the inhibitor, DBS. It is certain that calcium atoms contained in the protease must play an important role for the protease enzyme activity and its stability. Calcium atoms must have a great influence on the formation of protease-substrate complex, protease-compound complex and substrate-compound complex, because the protease, protein substrate and anionic compound would all be negatively charged in alkaline solutions. Builders for enzyme-containing detergents should be constructed to be insensitive to calcium ion.