They are two major categories of Yeast invertase; they include internal and external invertase. There is a clear similarity and marked disparities shown by properties of purified preparations if external and internal invertases of yeast that are designated by their location in relation to the cell membrane. There is resemblance between specific activity and molecular weight of both internal and protein moiety of external invertase.
However, they are differences between external and internal invertase; their molecular weights vary (external invertase MW=270,000 Daltons, internal invertase MW=135,000 Daltons). The compositions of amino acids are dissimilar with external invertase having cystine or cysteine. The internal enzymes do not have the same amino acids composition. However, the general structure and differences of enzymes are the same with differences in amino acids composition.