Thermostability variation in alleles of barley beta-amylase

Abstract Thermostability assays in conjunction with IEF and molecular mapping were used to identify three beta-amylase alleles (Bmyl-Sd1, -Sd2L, -Sd2H) in cultivated barley and an additional allele (Bmy1-Sd3) in an accession of wild barley Hordeum vulgare ssp. spontaneum. The four forms of beta-amylase exhibit different rates of thermal inactivation in barley extracts. This variation was shown to persist after the proteolytic processing of the enzyme that occurs during germination. Three forms of beta-amylase representing the range of thermostabilities were purified and shown to have T50 temperatures of 56·8°C for the Sd2L enzyme, 58·5°C for the Sd1 enzyme, and 60·8°C for the Sd3 beta-amylase from wild barley. Analysis of the relationship between beta-amylase thermostability and fermentability, i.e. the yield of fermentable sugars obtained from starch hydrolysis during brewing in 42 commercial malt samples suggests that increased thermostability results in more efficient starch degradation. Screening for specific beta-amylase alleles is proposed as a method for increasing fermentability in malting barley.

[1]  M. Williamson,et al.  Primary structure and differential expression of beta-amylase in normal and mutant barleys. , 1987, European journal of biochemistry.

[2]  Y. Okada,et al.  Construction of a plasmid used for the expression of a sevenfold-mutant barley beta-amylase with increased thermostability in Escherichia coli and properties of the sevenfold-mutant beta-amylase. , 1995, Journal of biochemistry.

[3]  D. Hardie,et al.  Control of carbohydrase formation by gibberellic acid in barley endosperm , 1975 .

[4]  R. Ray,et al.  Biochemical approaches of increasing thermostability of β‐amylase from Bacillus megaterium B6 , 1994, FEBS letters.

[5]  R. Kothari,et al.  Characterization of barley β-amylase for application in maltose production , 1992 .

[6]  R. Codd,et al.  Measurement of β-amylase in cereal flours and commercial enzyme preparations , 1989 .

[7]  W. Wallace,et al.  Release and activation of barley Beta-amylase by malt endopeptidases , 1992 .

[8]  C. Henson,et al.  A quantitative assessment of the importance of barley seed α-amylase, β-amylase, debranching enzyme, and α-glucosidase in starch degradation , 1991 .

[9]  Y. Okada,et al.  PCR cloning and sequencing of the beta-amylase cDNA from barley. , 1994, Journal of biochemistry.

[10]  D. D. Kosambi.  The estimation of map distances from recombination values. , 1943 .

[11]  B. Mikami,et al.  [Primary structure and function of beta-amylase]. , 1988, Seikagaku. The Journal of Japanese Biochemical Society.

[12]  M. Hendrickx,et al.  The influence of polyalcohols and carbohydrates on the thermostability of α‐amylase , 1994 .

[13]  D. Mather,et al.  Regions of the Genome That Affect Grain and Malt Quality in a North American Two-Row Barley Cross , 1997 .

[14]  W. Wallace,et al.  Measurement ofBeta-amylase in Malting Barley (Hordeum vulgareL.). I. Development of a Quantitative ELISA forBeta-amylase , 1997 .

[15]  E. Lander,et al.  Mapping mendelian factors underlying quantitative traits using RFLP linkage maps. , 1989, Genetics.

[16]  H. R. Taylor,et al.  DIASTATIC POWER IN MALTED BARLEY: CONTRIBUTIONS OF MALT PARAMETERS TO ITS DEVELOPMENT AND THE POTENTIAL OF BARLEY GRAIN BETA‐AMYLASE TO PREDICT MALT DIASTATIC POWER* , 1995 .

[17]  Ningyan Zhang,et al.  Characterization of germinated barley endoproteolytic enzymes by two-dimensional gel electrophoresis , 1995 .

[18]  J. Sacchettini,et al.  The 2.0-A resolution structure of soybean beta-amylase complexed with alpha-cyclodextrin. , 1993, Biochemistry.

[19]  E. Querol,et al.  Analysis of protein conformational characteristics related to thermostability. , 1996, Protein engineering.