I'm having a hard time making a distinction between simple and complex enzymes. the definitions I've found so far all say this:
Simple enzymes are enzymes that are only made out of protein, and complex enzymes are ones that, in addition to the protein portion, have a non-protein portion as well, which is called a co-enzyme/prosthetic group (I've seen both terms being used)
Does this mean that any protein that utilizes a co-factor, even if that co-factor is simply a co-enzyme or an activating metal, i.e., not an actual part of the enzyme's structure, is considered a complex enzyme? Or are the two terms restricted to the structure of the enzyme (i.e., whether they have prosthetic groups, be they organic or inorganic, or not)?