This invention relates generally to polypeptides and peptides having an amylase activity, e.g., enzymes, polynucleotides encoding the enzymes, the use of such polypeptides and peptides. In one aspect, the polypeptides having amylase activity have increased activity and stability at acidic, neutral and alkaline pH and increased temperature. In one aspect, the invention provides methods for producing an alcohol, for producing a high-maltose or a high-glucose syrup or a mixed syrup, for liquifying a starch-comprising composition, comprising use of polypeptides having amylase activity of the invention.