Abstract: Provided is a method for determining activity of arylsulfatase in an aqueous system, which comprises a step in which arylsulfatase is subjected to reaction with a substrate, from which fluorophore or chromophore is liberated by suffering an action of the arylsulfatase, in an aqueous reaction system having high ionic strength. Also, provided are a lactase preparation having a lactase activity of 4,000 NLU/g or more according to the FCC IV method and having an arylsulfatase activity of 0.1% or less of the lactase activity as the basis, in which the arylsulfatase activity has been determined by the method for determining activity of arylsulfatase in an aqueous system according to the fluorescence method of the present invention; a method for producing this preparation; and a dairy product which comprises using this preparation.

Abstract: An isoamylase having improved heat resistance and an industrial method for producing maltose from starch. The isoamylase is an isoamylase consisting of the amino acid sequence represented by SEQ ID NO: 1 or an isoamylase resulting from deletion, substitution, or insertion of one to several amino acid residues in the amino acid sequence represented by SEQ ID NO: 1, wherein at least valine at amino acid number 515 and methionine at amino acid number 570 are mutated to other amino acids.

Abstract: A method for producing a lactase-containing composition which is purified by selectively removing protease contaminating the lactase using simple and easy means; a lactase-containing composition; and a dairy product containing the lactase-containing composition. A method for producing a lactase-containing composition having a reduced protease content includes: dissolving a composition containing lactase and protease in an aqueous salt solution having an electric conductivity of from 2 to 45 mS/cm; bringing the resultant solution into contact with an ion exchange resin; and collecting a fraction which is not adsorbed onto the ion exchange resin.

Abstract: An isoamylase having improved heat resistance and an industrial method for producing maltose from starch. The isoamylase is an isoamylase consisting of the amino acid sequence represented by SEQ ID NO: 1 or an isoamylase resulting from deletion, substitution, or insertion of one to several amino acid residues in the amino acid sequence represented by SEQ ID NO: 1, wherein at least valine at amino acid number 515 and methionine at amino acid number 570 are mutated to other amino acids.

Abstract: A lactase preparation includes lactase and has a lactase activity of 4,000 NLU/g or more according to the FCC IV method, wherein the lactase originates from a lactase gene of yeast, and wherein the lactase preparation has an arylsulfatase activity of 0.1% or less based on the lactase activity, in which the arylsulfatase activity (unit: U/g) is determined and calculated.

Abstract: A method for producing a lactase-containing composition which is purified by selectively removing protease contaminating the lactase using simple and easy means; a lactase-containing composition; and a dairy product containing the lactase-containing composition. A method for producing a lactase-containing composition having a reduced protease content includes: dissolving a composition containing lactase and protease in an aqueous salt solution having an electric conductivity of from 2 to 45 mS/cm; bringing the resultant solution into contact with an ion exchange resin; and collecting a fraction which is not adsorbed onto the ion exchange resin.

Abstract: Provided is a means for accurately analyzing a protease by electrophoresis. Disclosed is an electrophoretic analysis method for analyzing a protease-containing sample, is characterized by exposing a sample containing a protease to be analyzed, to pH conditions under which the protease is rapidly deactivated, and then subjecting the sample to electrophoresis.

Abstract: Provided is a method for determining activity of arylsulfatase in an aqueous system, which comprises a step in which arylsulfatase is subjected to reaction with a substrate, from which fluorophore or chromophore is liberated by suffering an action of the arylsulfatase, in an aqueous reaction system having high ionic strength. Also, provided are a lactase preparation having a lactase activity of 4,000 NLU/g or more according to the FCC IV method and having an arylsulfatase activity of 0.1% or less of the lactase activity as the basis, in which the arylsulfatase activity has been determined by the method for determining activity of arylsulfatase in an aqueous system according to the fluorescence method of the present invention; a method for producing this preparation; and a dairy product which comprises using this preparation.

Abstract: Provided is a means for accurately analyzing a protease by electrophoresis. Disclosed is an electrophoretic analysis method for analyzing a protease-containing sample, is characterized by exposing a sample containing a protease to be analyzed, to pH conditions under which the protease is rapidly deactivated, and then subjecting the sample to electrophoresis.