title: Characterization of a novel alpha-amylase from Lipomyces kononenkoae and expression of its gene (LKA1) in Saccharomyces cerevisiae.
abstract: A highly active alpha-amylase (76,250 Da) secreted by the raw starch-degrading yeast Lipomyces kononenkoae strain IGC4052B was purified and characterized. Using high performance liquid chromatography (HPLC), end-product analysis indicated that the L. kononenkoae alpha-amylase acted by endo-hydrolysis on glucose polymers containing alpha-1,4 and alpha-1,6 bonds, producing mainly maltose, maltotriose and maltotetraose. The following NH2-terminal amino acids were determined for the purified enzyme: Asp-Cys-Thr-Thr-Val-Thr-Val-Leu-Ser-Ser-Pro- Glu-Ser-Val-Thr-Gly. The L. kononenkoae alpha-amylase-encoding gene (LKA1), previously cloned as a cDNA fragment, was expressed in Saccharomyces cerevisiae under the control of the PGK1 promoter. The native signal sequence efficiently directed the secretion of the glycosylated protein in S. cerevisiae. De-glycosylation of the enzyme indicated that post-translational glycosylation is different in S. cerevisiae from that in L. kononenkoae. Zymogram analysis indicated that glycosylation of the protein in S. cerevisiae had a negative effect on enzyme activity. Southern-blot analysis revealed that there is only a single LKA1 gene present in the genome of L. kononenkoae.
authors.affiliation: Department of Microbiology, University of Stellenbosch, South Africa.
authors.forename: A J
authors.initials: AJ
authors.lastname: Steyn
authors.forename: I S
authors.initials: IS
authors.lastname: Pretorius
mesh_terms: D000595:Amino Acid Sequence; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D015966:Gene Expression Regulation, Fungal; D008670:Metals / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D004718:Saccharomycetales / Q000201:enzymology*; D013213:Starch / Q000378:metabolism; D013379:Substrate Specificity; D000516:alpha-Amylases / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
chemical_list: D008670:Metals; D011994:Recombinant Proteins; D013213:Starch; D000516:alpha-Amylases