Name: enzyme helpers: metals, vitamins, and more
Uploaded: 2019-07-31T14:21:57.000Z
Duration: 1 min 27 s
Channel: JoVE

In vielen Fällen benötigen Enzyme zusätzliche Moleküle, sogenannte Cofaktoren, um zu funktionieren.
 Diese Hilfsmoleküle können entweder als Metallionen oder als organische Nicht-Proteinmoleküle klassifiziert werden.
 Beispielsweise bindet der Cofaktor Magnesium während des ersten Schrittes der Glykolyse an ATP, wodurch die Bindung zwischen zwei der Phosphatgruppen gestärkt wird.
 Diese Aktion ermöglicht der letzten Phosphatgruppe eine leichter durch die Enzym Hexokinase freigesetzt zu werden, wodurch Glucose in Glucose-6-phosphat umgewandelt wird.
 Daher bindet sich Magnesium als Cofaktor an das ATP, und erhöht dessen Effizienz.
 Die andere Untergruppe der Cofaktoren, die Coenzyme, sind organische Verbindungen, in der Regel Derivate von Vitaminen.
 Beispielsweise ist Vitamin C ein wichtiges Coenzym bei der Synthese des Proteinkollagens.
 Wenn sich Kollagen an seine Enzym Hydroxylase bindet, bindet sich dann Vitamin C an das Enzym und spendet eine Hydroxylgruppe.
 Jetzt kann die hydrolysierte Hydroxylase dazu beitragen, die Form des Kollagens in seine endgültige dreifache Helixstruktur zu ändern, die für die Aufrechterhaltung wichtiger Körpergewebe wesentlich ist.

Tong, Liang. "Struktur und Funktion von Biotin-abhängigen Carboxylasen." Zelluläre und molekulare Lebenswissenschaften 70, Nr. 5 (2013): 863-891. [<a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3508090/">Quelltext</a>]

Yang, Wei, Jae Young Lee und Marcin Nowotny. "Herstellung und Zerkleinerung von Nukleinsäuren: Zwei-Mg2+-Ionenkatalyse und Substratspezifität." Molekulare Zelle 22, Nr. 1 (2006): 5-13. [<a href="https://doi.org/10.1016/j.molcel.2006.03.013">Quelltext</a>]

kofaktoren und coenzyme

Cofactors and Coenzymes

Enzyme benötigen zusätzliche Komponenten für eine einwandfreie Funktionsweise. Es gibt zwei Klassen solcher Moleküle: Kofaktoren und Koenzyme. Kofaktoren sind Metallionen und Coenzyme sind organische Moleküle, die keine Proteine sind. Beide Arten dieser Hilfsmoleküle können fest an das Enzym gebunden sein oder nur dann gebunden werden, wenn das Substrat bindet.
 
 Kofaktoren sind in ca. 30 % aller reifen Proteine vorhanden. Sie werden häufig in ein gefaltetes Enzym eingebaut und sind an der katalytischen Aktivität des Enzyms beteiligt. Magnesium ist ein essenzieller Kofaktor für über 300 Enzyme des menschlichen Körpers. Auch für die DNA-Polymerase ist es notwendig. In diesem Fall hilft das Magnesium-Ion bei der Bildung der Phosphodiester-Bindung des DNA-Gerüsts. Eisen, Kupfer, Kobalt und Mangan sind weitere übliche Kofaktoren.
 
 Viele Vitamine sind Coenzyme. Sie sind keine Proteine, sondern organische Hilfsmoleküle für Enzyme. So ist beispielsweise Biotin, ein Typ der B-Vitamine, in vielen Enzymen wichtig, die Kohlenstoffdioxid von einem Molekül auf ein anderes übertragen. Biotin, Vitamin A und andere Vitamine müssen mit der Nahrung aufgenommen werden, da sie nicht von menschlichen Zellen hergestellt werden können.

Kofaktoren und Coenzyme

Enzyme benötigen für ihre einwandfreie Funktion zusätzliche Komponenten. Es gibt zwei solche Klassen von Molekülen: Cofaktoren und Coenzyme. Cofaktoren sind metallische Ionen ...

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enzyme helpers: metals, vitamins, and more

Enzyme helpers are needed for many enzymes to work properly. These helpers fall into two groups: cofactors and coenzymes. Cofactors are metallic ions, while coenzymes are non-protein organic molecules. Both can be tightly bound to an enzyme or attach only when the substrate binds.

Cofactors are common in mature proteins, appearing in about 30% of them. They are often added as the enzyme folds and help with catalytic activity. Magnesium is one important cofactor, and it is needed by more than 300 enzymes in the human body, including DNA polymerase. In DNA polymerase, magnesium helps form the phosphodiester bond in the DNA backbone. Iron, copper, cobalt, and manganese are other common cofactors.

Many coenzymes come from vitamins. These organic helper molecules assist enzymes during reactions. Biotin, which is a B vitamin, helps several enzymes move carbon dioxide from one molecule to another. Vitamin A and other vitamins must come from the diet because human cells cannot make them.

Enzyme Helpers: Metals, Vitamins, and More

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Substrate Effects on Enzyme Rates

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cofactors and coenzymes

Enzyme helpers are needed for many enzymes to work properly. These helpers fall into two groups: cofactors and coenzymes. Cofactors are metallic ions, while coenzymes are non-protein organic molecules. Both can be tightly bound to an enzyme or attach only when the substrate binds. Cofactors are common in mature proteins, appearing in about 30% of them. They are often added as the enzyme folds and help with catalytic activity. Magnesium is one important cofactor, and it is needed by more than...

key terms and concepts

Learn how cofactors and coenzymes help enzymes work, from magnesium in DNA polymerase to biotin and other vitamin-based helpers.

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Enzyme Helpers: Metals, Vitamins, and More

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