Three things that can denature enzymes are temperature, pH level and salt concentrations. Enzymes are proteins; as with all proteins, enzymes work only in certain optimal environments. These optimal environments include certain temperature ranges, specific pH levels and particular salt concentrations.
If an enzyme is not in its optimal environment, it may not work well or even at all. Enzymes become denatured, or disfigured, in nonoptimal environments. Denatured enzymes lose their natural three-dimensional folded shapes.
Many enzymes do not work well at high temperatures. An increase in temperature generally favors enzyme function, but at temperatures above 40 degrees Celsius, many animal enzymes no longer function. A shift in pH level affects hydrogen bonds, a weak type of bond that connect parts of the enzyme to one another; this changes the enzyme's shape. Changes in salinity affect the R-group bonding in amino acids, the building blocks of all proteins. These R groups, also called amino acid side chains, interact with one another to produce a protein's three-dimensional shape.