Diverse properties of external and internal forms of yeast invertase derived from the same gene

It has been shown by genetic analysis that the external and internal invertases from Saccharomyces cerevisiae share a common structural gene [Taussig, R., & Carlson, M. (1983) Nucleic Acids Res. 11, 1943-1954]. However, the only amino acid composition of these two forms of invertase reported to date has revealed extensive differences [Gascon, S., Neumann, N.P., & Lampen, J.O. (1968) J. Biol. Chem. 243, 1573-1577]. We have found from amino acid analyses of both enzymes and sodium dodecyl sulfate-polyacrylamide gel analysis of their cyanogen bromide peptides that they are most likely identical in their amino acid sequence. However, the invertases exhibit dramatically different physical properties, particularly in their stability. The most striking difference was in their renaturation following guanidine treatment where it was shown that inactivated external invertase could be renatured completely. Endo-beta-N-acetylglucosaminidase H treated external invertase was restored to 40% of its original activity while internal invertase remained completely inactive. The observed differences may be attributed to the presence and absence of the oligosaccharide moiety in the external and internal invertases, respectively.