DNA聚合酶是通过将脱氧核糖核苷酸添加到预先存在的底漆的3'-OH端来催化DNA的酶。有不同类型的DNA聚合酶。分子生物学中使用的大多数DNA聚合酶是原核DNA聚合酶。Klenow片段和T4 DNA聚合酶是具有核酸起源的两种类型的DNA聚合酶。klenow碎片是从乳沟产生的大片段E.coliDNA聚合酶1分成两个细菌蛋白酶枯草蛋白分成两个片段。T4 DNA聚合酶是噬菌体T4的DNA聚合酶1。Klenow和T4 DNA聚合酶均具有5'→3'聚合酶和3'→5'exonucleaseactivity. They both lack 5′→3′ exonuclease activity, making them more suitable for many applications in molecular biology.
What is Klenow?
Klenow fragment is a DNA polymerase that is useful in molecular biology. WhenE. coliDNA polymerase 1 undergoes proteolytic digestion by bacterial protease, subtilisin, it results in two fragments: one is a large fragment, and the other one is a small fragment. Klenow fragment is the large fragment which is 68 kDa in size. Klenow fragment has 5′→3′ polymerase and 3′→5′ exonuclease (proofreading) activities of DNA Pol I. The 3′→5′ exonuclease activity of the Klenow fragment facilitates the removal of incorrectly added bases as polymerization progresses. Klenow fragment does not contain 5′→3′ exonuclease activity, which is shown by full-length or intactE. coliDNA聚合酶1.仅需单独使用聚合活性时，这是有利的。Klenow片段用于填充5'突出，探针的合成，测序DNA，双链DNA的合成，cDNA第二链的合成和定点诱变。
In certain applications, the 3′→5′ exonuclease activity of the Klenow fragment also becomes undesirable. It can be removed by introducing a mutation to the gene that codes for Klenow fragment. The resulting Klenow fragment is known as exo-Klenow fragment. Therefore, exo-Klenow fragment has only the 5′→3′ polymerase activity ofE. coli聚合酶1。
T4 DNA polymerase is a DNA polymerase that catalyzes the synthesis of DNA. It is a protein coded by Bacteriophage T4. Structurally, T4 DNA polymerase is an 898 amino acid residue protein (molecular weight of 103.6 kDa). It requires a template and a primer to catalyze the synthesis.
与Klenow片段相似，T4 DNA聚合酶具有5'→3'聚合酶和3'→5'外核酸酶活性。此外，它也缺乏5'→3'外切核酸酶活性。T4 DNA聚合酶可用于填充DNA片段的5'缩端。它通常也用于双链DNA的5'端或3'端标签。T4 DNA聚合酶经常用于钝化克隆。T4 DNA聚合酶的3'→5'外切核酸酶（校对）活性比Klenow片段强（超过200倍）。最重要的是，T4 DNA聚合酶具有较高的加工性（每秒400个核苷酸）。
What are the Similarities Between Klenow and T4 DNA Polymerase?
- Klenow and T4 DNA polymerase are two prokaryotic polymerases.
- They do not exhibit 5′→3′ exonuclease activity.
- These enzymes can be heat inactivated at 750
What is the Difference Between Klenow and T4 DNA Polymerase?
The key difference between Klenow and T4 DNA polymerase is the origin of each enzyme. Klenow fragment is originated from a bacterium while T4 DNA polymerase is originated from a bacteriophage which is a virus. T4 DNA polymerase has a high processivity than Klenow fragment. Moreover, T4 DNA polymerase has a strong proofreading activity than the Klenow fragment. Thus, this is another difference between Klenow and T4 DNA polymerase.
摘要 - Klenow vs T4 DNA聚合酶
Klenow fragment is a large fragment of E. coli DNA polymerase 1. It has only 5′→3′ polymerase and 3′→5′ exonuclease activities. It lacks 5′→3′ exonuclease activity of intact E. coli DNA pol 1. Therefore, Klenow fragment is a bacterial polymerase. On the other hand, T4 DNA polymerase is a polymerase coded by the bacteriophage T4. Similar to the Klenow fragment, it contains both 5′→3′ polymerase and 3′→5′ exonuclease activities, and it lacks 5′→3′ exonuclease activity. However, T4 DNA polymerase has high processivity and high proofreading activity than the Klenow fragment. So, this is the key difference between Klenow and T4 DNA polymerase.
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