Difference Between Metalloenzymes and Metal Activated Enzymes

Thekey differencebetween metalloenzymes and metal activated enzymes is that themetalloenzymes have a firmly bound metal ion as the cofactor whereas the metal ions in metal activated enzymes are not firmly bound.

The activity of some enzymes depends on metal ions because these metal ions act as cofactors. These enzymes are in two major categories as metalloenzymes and metal activated enzymes. Therefore, these enzymes are different from each other according to the presence or absence of tightly bound metal ions. Let us discuss more details on these enzymes.

CONTENTS

1.Overview and Key Difference
2.What are Metalloenzymes
3.What are Metal Activated Enzymes
4.并排比较 - 金属酶与金属激活酶以表格形式
5.概括

What are Metalloenzymes?

金属酶是含有紧密结合的金属离子的酶。该金属离子形成坐标covalent bondswith theamino acidsof theenzymeor with aprosthetic group. Further, it acts as a coenzyme and imparts the activity of the enzyme. When considering the location of the metal ion in the enzyme, it usually occurs in a specific region on the enzyme surface. Therefore, the ion does not disturb the binding of the substrate with the active site. Sometimes, enzymes require more than one metal ion for its activity. In rare occasions, they require two different metal ions as well. The most common metals that involve in this are Fe, Zn, Cu, and Mn. The metalloenzymes containing metal centers other than iron (non-heme centers) are wide spread in nature.

Examples of metalloenzymes:

• Amylase, thermolysin are bound with Ca²⁺ions
• Dioldehydrase, glycerol dehydratase are bound with Co²⁺
• Cytochrome c oxidase, dopamine-b-hydroxylase contains Cu²⁺
• Catalase, nitrogenase, peroxidase, succinate dehydrogenase contains Fe²⁺
• 精氨酸酶，组氨酸 - 氨基酸酯裂解酶，丙酮酸羧化酶含有Mn²⁺

What are Metal Activated Enzymes?

金属活化的酶是由于金属离子的存在而具有增加活性的酶。大多数情况下，这些金属离子是单价或二价。但是，这些离子与金属酶中的酶没有紧密结合。金属可以激活底物，因此直接与酶的活性接合。这些酶需要过量的金属离子。例如：比酶浓度高约2-10倍。这是因为他们不能永久与金属离子键合。但是，这些酶在纯化过程中失去了活性。

Examples of meta activated enzymes:

• Pyruvate kinase requires K⁺
• Phosphotransferases requires Mg²⁺or Mn²⁺

What is the Difference Between Metalloenzymes and Metal Activated Enzymes?

The metalloenzymes are enzymes which contain a tightly bound metal ion. As a unique characteristic, they have a firmly bound metal ion as the cofactor. Moreover, these enzymes require either one or two metal ions bound on to a specific region of the surface of the enzyme for their activity. Metal activated enzymes are enzymes that have an increased activity due to the presence of metal ions that are not firmly bound. It is the key difference between metalloenzymes and metal activated enzymes. That is, unlike the metalloenzymes, the metal-activated enzymes do not have a firmly bound metal ion as the cofactor. In addition to that, these enzymes require a high concentration of metal ions around them.

概括– Metalloenzymes vs Metal Activated Enzymes

活性取决于金属离子的存在的酶有两种类型。它们是金属酶和金属活化酶。金属酶和金属活化酶之间的差异在于，金属酶具有牢固结合的金属离子作为辅因子，而金属活化酶中的金属离子没有牢固结合。

Reference:

1. “Metalloprotein.” Wikipedia, Wikimedia Foundation, 23 July 2018.Available here
2. “Metalloenzyme.” Egyptian Journal of Medical Human Genetics, Elsevier.Available here

Image Courtesy:

1.’Enzyme action’By Muessig – Own work,(CC BY-SA 3.0)viaCommons Wikimedia