Abstract: A method for the assay of .alpha.-amylase activity, which comprises adding an .alpha.-amylase-containing sample to maltohexaitol or maltohexaonic acid used as substrate, reacting, at the same time or subsequent to the addition, .alpha.-glucosidase with the resulting mixture, and determining the reaction product to assay the .alpha.-amylase activity.

Abstract: A method for the preparation of a novel recombinant DNA, which comprises (1) cleaving with an endonuclease a temperate phage DNA having an endonuclease-sensitive region not in the DNA segment participating in the replication of phage DNA and the integration of phage DNA into a host chromosome but at least in the DNA segment carrying genetic information for the coat protein production and another DNA carrying intended genetic information, (2) adding DNA-ligase to the mixture of both cleft DNA's, and (3) recovering from the mixture a phage DNA having its coat protein producing ability deleted by the replacement of the DNA segments carrying genetic information for the coat protein production with a DNA fragment carrying the intended information.

Abstract: A method for preparing a novel recombinant DNA, which comprises (1) cleaving with an endonuclease a phage DNA having an endonuclease-sensitive region not in the DNA segment participating in temperate phage DNA replication and integration of DNA into a host chromosome but in other DNA segments, a temperate phage DNA having an endonuclease-sensitive region in the DNA segment carrying genetic information for the production of coat protein, and a DNA carrying the intended genetic information, (2) mixing together all fragments produced by said cleaving, (3) adding DNA ligase to the mixture, and (4) recovering from the resulting mixture a phage DNA having its coat protein producing ability deleted by the replacement of the DNA segment carrying genetic information for coat protein production with a DNA fragment carrying the intended genetic information.

Abstract: A novel bacteriophage whose DNA molecule has endonuclease-sensitivity only in the DNA region carrying genetic information for the production of phage coat proteins can be obtained by isolating an endonuclease-resistant mutant from one of the lambdoid bacteriophages and mating the resulting bacteriophage with a lambdoid phage having endonuclease-sensitivity in the DNA region carrying genetic information for the production of coat proteins.

Abstract: Creatinine amidohydrolase and creatine amidinohydrolase can be obtained by culturing a strain belonging to Genus Flavobacterium, Genus Micrococcus or Genus Corynebacterium and having an ability to produce creatinine amidohydrolase and creatine amidinohydrolase in the presence of creatinine, creatine or a mixture thereof and separating creatinine amidohydrolase and creatine amidinohydrolase from the cultured fluid.