What is the general function of enzymes in the human body?
Enzymes speed up, and simply drive the chemical reactions within the bodies cells.
Without enzymes, life would not exist. Enzymes are found in a variety of cells, and perform a vast amount of specific and complex tasks. Enzymes are found and used in the digestive process for example, which some (not all) include amylase, lipase, pepsin, trypsin and many more.
Hope this helped.
Here is a video showing a demonstration of enzyme activities.