A series of new maltase mutants were sseparated from yeast species that carried MAL4 gene.Those mutants can not ferment with maltose,sugar and α methylglucogate.But the most of revertant that was separated from these mutants recovered again the ability of fermenting the above sugars,and produced the maltase amounts same as their paental generation.However,some of revertants fermented maltose slowly,and the amount of enzymes was less 24 times than their parental generation.The genetics research pointed out that the revertant is not real revertant,but carries extra an inhibitory gene.This inhibitory gene inhibits the allele mal4 in the revertant Z-4.The results showed that the gene MAL4 is a kind of regulatory gene,therefore the gene MAL4 may code the regulatory protein.The regulatory protein may play a positive regulating role in synthesizing the maltase.
