i dont know the max number possible, but i know it depends on the situation. some examples of factors involved: what kind of cell it is: Some enzymes are made only in certain types of white blood cells, for instance, and some are made only in certain types of epithelial cells. what the cell is doing at the moment: for example, if that white blood cell is ingesting a foreign particle, it might use enzymes that are different from when that same cell is actually breaking it up.. and even different enzymes if it presents the particles on its surface. a skin cell might have enzymes that help it to grow hair, or to help it make sweat, or to stick together closely with other cells.. if the cell is injured it might also change up the enzymes it expresses. In any case, the enzymes might not even exist in the cell if they are not needed at that moment. other stuff: some enzymes are sort of pro-enzymes and might be hanging out in the cell and may need to be processed before they become "activated" .. would you count those enzymes? also, since enzymes are proteins, they would need to be created using the DNA in the cell. remember not all enzymes that a cell can use are always existing in that cell. they exist after they are translated from dna, when they are needed. then, there are some enzymes that are involved in unwinding the DNA, to give other things access to the DNA, so that the enzyme can be created. That is just a few examples of why its hard to tell. Also, although the human genome is known, how all the genes are expressed is not known, and im guessing that includes genes that help make enzymes. Its kind of like asking "how many kinds of people are in a company." They may have the common framework of being a company, but theres no telling how many different kinds of people in it unless you know everything the company does, and when and how it does it.