脱氧核糖核酸酶 I 来源于牛胰腺

Analysis Note

Protein determined by biuret.

Application

用于从蛋白质样品中除去 DNA。

DNAse I from Sigma has been compared with human urine-derived interleukin 1 inhibitor for the ability to hydrolyze [¹⁴C]DNA [¹⁴C]DNA.^[2] It has also been used to cleave a 139 base pair Hind III/Nci I restriction fragment to investigate the stability of the enzyme for use in footprinting experiments. DNase I is widely used as a footprinting agent for studying drug and protein binding to DNA.^[5]

Deoxyribonuclease I from bovine pancreas has been used in a study to investigate a new approach to obtaining high-activity RNase, DNase, cholesterolesterase, and trypsin from cattle pancreas. Deoxyribonuclease I from bovine pancreas has also been used in a study to investigate the isolation and further characterization of carp liver DNase.

Preparation Note

The enzyme powder may be reconstituted in water or any buffer at pH 4.0-9.0, except phosphate buffer. Calcium chelators should be avoided. 10 mg/mL solution of DNAse I in 0.15 M NaCl may lose <10% of its activity when stored for a week in aliquots at −20 °C. The same solutions stored in aliquots at 2-8 °C can lose approximately 20% activity. It remains active for up to five hours at 60 °C between pH 5 and 7, and loses activity in <10 minutes at 68 °C. It loses activity at the rate of 6%/hour in acetate buffer (pH 5.0) and tris buffer ((pH 7.2) at 1 mg/mL concentration.

Unit Definition

One Kunitz unit will produce a ΔA₂₆₀ of 0.001 per min per mL at pH 5.0 at 25 °C, using DNA, Type I or III as substrate.

Physical form

含氯化钙的冻干粉

Biochem/physiol Actions

DNase I is an endonuclease that acts on phosphodiester bonds adjacent to pyrimidines to produce polynucleotides with terminal 5′-phosphates. In the presence of Mg²⁺, DNAse I cleaves each strand of DNA independently and the cleavage sites are random. Both DNA strands are cleaved at approximately the same site in the presence of Mn²⁺.^[6] The pH optimum lies between 7 and 8. Divalent cations such as Mn²⁺, Ca²⁺, Co²⁺, and Zn²⁺ are activators of the enzyme.^[7] A concentration of 5 mM Ca²⁺ stabilizes the enzyme against proteolytic digestion. DNAse I from bovine pancreas consists of four chromatographically distinguishable components, A, B, C, and D, with their molar ratios being 4:1:1 respectively. Only minor amounts of D are found.^[4] 2-Mercaptoethanol, chelators, sodium dodecyl sulfate (SDS)^[3] and actin^[1] are known to inhibit the enzyme activity.

性质

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