Submitted to: Plant Physiology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2003
Publication Date: 9/20/2003
Citation: Clark, S.E., Henson, C.A., Hayes, P.M. 2003. Effects of single nucleotide polymorphisms in beta-amylase 1 alleles from barley on fuctional properties of the enzymes. Plant Physiology and Biochemistry. 41:798-804. Interpretive Summary: Barley malt enzymes break large starch molecules down to small sugars. Some of these sugars are used by yeast to produce alcohol. Certain stages of brewing require temperatures that are high enough to inactivate the malt enzymes responsible for breaking down starch. The work conducted here demonstrated the existence of genetic variation in the gene that encodes one of the heat-sensitive enzymes. Furthermore, this work determined which allelic variant encoded an enzyme with enhanced stability and function. This research will allow plant breeders to make future crosses using only cultivars with the most desirable genes.
Technical Abstract: Differences in extractable beta-amylase activities exist between enzymes from malt and feed barleys. Others have documented few differences in the coding regions and large differences in the noncoding regions of genomic DNA for endosperm specific beta-amylases from malt and feed barleys, and correlated differences in one intron with activity levels in seeds (Erkkila et al., 1998) The work reported in this study demonstrates that differences in the coding regions of beta-amylase1 from a malt ('Morex) and a feed ('Steptoe) barley significantly affected the phenotype (total activity of the enzyme, response to exogenous proteins, and thermostabiltiy) of the enzymes. We evaluated the contribution of the three single nucleotide polymorphisms that caused differences in the amino acid sequences at positions 115, 165, and 430. Two single nucleotide polymorphisms (positions 115 and 430) were found to impact the enzymatic activity of beta-amylase. The single nucleotide polymorphism at position 165 had a variable effect on enzyme activity. The contributions of the three single nucleotide polymorphisms to beta-amylase thermostability were temperature dependent.