Abstract: A restriction enzyme is obtained by cultivating a strain of Brevibacterium linens and recovering the restriction enzyme.

Abstract: SP6 bacteriophage RNA polymerase is produced by cultivating a new microorganism (particularly new strains of Escherichia coli) harboring a plasmid that carries SP6 bacteriophage RNA polymerase gene and recovering SP6 bacteriophage RNA polymerase from the culture broth. SP6 bacteriophage RNA polymerase gene is provided as are new microorganisms harboring a plasmid that carries SP6 bacteriophage RNA polymerase gene.

Abstract: A novel restriction endonuclease SplI which has the following physicochemical properties:(1) recognizing the following base sequences in double-stranded deoxyribonucleic acid ##STR1## and cleaving said sequences in the phosphodiester bonds between C and G as indicated with the vertical arrows to produce DNA fragments having one strand comprising four bases at the 5'-terminal;(2) cleaving double-stranded deoxyribonucleic acid .lambda.-DNA in one position, Col El in two positions and .phi.x 174 RF in two positions;(3) being activated with 5 to 20 mM Mg.sup.2+ ; and(4) exhibiting an activity at a NaCl concentration of 0 to 200 mM;and a process for the production of the restriction endonuclease SplI which comprises culturing a restriction endonuclease SplI-producing alga belonging to the genus Spirulina, collecting the cells, obtaining a cell-free extract therefrom the separating and purifying the restriction endonuclease SplI.

Abstract: An enzyme composition comprising a series of enzymes used for DNA base sequence analysis by gel electrophoresis and a dihydric alcohol.

Abstract: The invention provides restriction endonuclease Mf1 I capable of recognizing the base sequence as shown below on a double-stranded DNA molecule and cleaving the DNA chain at the arrow-marked positions, but has no such action when A is methylated5'--Pu.dwnarw.GATC Py--3'3'--Py CTAG.uparw.Pu--5'(wherein A represents adenosine, G guanosine, T thymidine, C cytidine, Pu adenosine or guanosine, and Py thymidine or cytidine). The restriction endonuclease is produced by culturing Microbacterium flavum IAM 1642, FERM BP-938 in a culture medium and recovering it from the culture.

Abstract: A process for producing a restriction endonuclease capable of recognizing the nucleotide sequence ##STR1## (wherein A, C, G and T represent adenosine, cytidine, guanosine and thymidine, respectively) on a DNA chain and specifically cleaving the double-stranded chain at the arrow-marked positions. This process comprises growing a microorganism belonging to the genus Halococcus and capable of producing said restriction endonuclease, and collecting the enzyme thus formed from the culture broth.

Abstract: A restriction endonuclease having the ability to recognize the same base sequence and cleavage sites as SacII and SstII can be produced from Gluconobacter and isolated in pure form because no other restriction enzyme is formed.