VIEW ARTICLE    DOI: 10.1094/ASBCJ-53-0182

Use of Glucagon and Insulin as Tools to Study Metabolic Interrelationships in Brewing Yeasts (1). E. J. Lodolo (2), E. S. C. O'Connor-Cox, and B. C. Axcell, South African Breweries, Brewing Research and Development Department, P.O. Box 782178, Sandton 2146, South Africa. (1) Partially presented at the 1994 American Society of Brewing Chemists Convention, Toronto, Ontario, Canada. (2) Corresponding author. J. Am. Soc. Brew. Chem. 53(4):182-190, 1995. Accepted February 28, 1995.

It has been reported that glycogen contributes to mitochondrial development in maltose-inducible yeast strains. Previous work indicated that the two glycogen effector hormones, glucagon and insulin, functioned as expected in our yeast strain. Separate studies with carbonyl cyanide-m-chlorophenylhydrazone (CCCP) showed that this mitochondrial membrane ATP uncoupler severely affected this yeast. To further elucidate the role of mitochondria in brewing yeast during practical brewing conditions and to verify the possible interrelationship between glycogen metabolism and mitochondrial development, we inhibited the mitochondrial membrane proton pump with CCCP in the presence of insulin. Insulin alleviated the inhibitory effects of CCCP by increasing lipid biosynthesis, yeast growth, maltose and maltotriose uptake, free amino nitrogen utilization, and protein synthesis, whereas end acetaldehyde, sulfur dioxide, and diacetyl concentrations were reduced. The glycogen content was not significantly increased in the presence of insulin and CCCP. Glucagon severely affected cellular fatty acid concentrations. The observed effects of the hormones were highly dependent on the physiological condition and growth state of the yeast. We postulate that these mammalian hormones function in yeast as many evolutionary commonalties exist. A proposed mechanism for hormone function is suggested. Keywords: CCCP, Glucagon, Glycogen, Insulin, Mitochondria, Yeast