생화학 15단원 화학반응에 의한 효소의 조절 (카이네이스, 자이모겐) 요약정리

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• 1. Protein Kinases and Phosphatases

  Phosphorylation 반응을 촉매하는 효소들을 kinase라고 부르고 이들은 ATP를 사용하여 ATP를 ADP로 함과 동시에 phosphate group을 protein에 붙인다. 반면 dephosphorylation 반응을 촉매하는 효소들을 phosphatase라고 부른다. 많은 protein들이 phosphorylation 됨에 따라 activity를 가지게 되므로 많은 protein들의 activity는 protein kinase와 protein phosphatase의 activity에 따라 조절된다.

• 2. Regulation of Protein Activity by Phosphorylation

  Phosphorylation은 target protein의 activity를 조절하는데 매우 효과적이다. Phosphorylation reaction은 free energy의 변화가 크고, phosphate group은 protein에 연결된 상태에서 2개의 negative charge를 가져 protein의 conformation 변화와 electrostatical interaction에 큰 영향을 미칠 수 있다. 또한 phosphorylation과 dephosphorylation의 반응 속도를 적절히 조절할 수 있어 원하는 시간에 맞춰 조절할 수 있다.

• 3. Zymogen Activation

  어떤 효소의 경우 처음 만들어진 peptide chain이 folding된 후에도 효소 activity가 없다가 몇 peptide bond가 끊어진 후에 효소 activity를 가지는 경우가 있다. 이 경우 peptide bond가 끊어지기 전의 처음 folding된 효소 activity가 없는 protein을 zymogen이나 proenzyme이라고 부른다. Zymogen은 생체 내에서 많은 역할을 하는데 가령 digestive enzyme이 zymogen의 형태로 만들어지는 것이나 blood가 clotting 되는 경우 혈액이 빨리 굳어야 하므로 zymogen이 신속하게 peptide bond를 끊어 굳게 하는 것, insulin의 전구체인 proinsulin이나 collagen의 전구체인 procollagen, developmental process와 programmed cell death에서 역할하는 zymogen 등이 있다.

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• 1. Protein Kinases and Phosphatases

  Protein kinases and phosphatases are essential regulatory enzymes that play a crucial role in cellular signaling pathways. Protein kinases catalyze the addition of phosphate groups to specific amino acid residues on target proteins, often leading to changes in their activity, localization, or interactions. Conversely, protein phosphatases remove these phosphate groups, restoring the original state of the target proteins. The delicate balance between kinase and phosphatase activities is crucial for maintaining homeostasis and coordinating various cellular processes, such as metabolism, cell growth, differentiation, and apoptosis. Dysregulation of these enzymes has been implicated in numerous diseases, including cancer, neurological disorders, and metabolic syndromes. Understanding the mechanisms and regulation of protein kinases and phosphatases is an active area of research, as it holds great potential for the development of targeted therapies and the advancement of our understanding of complex biological systems.

• 2. Regulation of Protein Activity by Phosphorylation

  Phosphorylation is a ubiquitous post-translational modification that plays a pivotal role in the regulation of protein activity and function. By adding a phosphate group to specific amino acid residues, such as serine, threonine, or tyrosine, phosphorylation can induce conformational changes, alter protein-protein interactions, and modulate enzymatic activity. This dynamic process allows cells to rapidly respond to various stimuli and coordinate complex signaling cascades. Phosphorylation can lead to the activation or inhibition of target proteins, as well as changes in their subcellular localization, stability, and interactions with other biomolecules. The reversible nature of phosphorylation, mediated by the opposing actions of kinases and phosphatases, provides a versatile and tightly regulated mechanism for fine-tuning cellular processes. Dysregulation of phosphorylation-dependent signaling pathways has been implicated in numerous diseases, including cancer, neurological disorders, and metabolic diseases. Elucidating the intricate mechanisms and networks governing phosphorylation-mediated regulation is a crucial area of research, as it holds great promise for the development of targeted therapies and the advancement of our understanding of complex biological systems.

• 3. Zymogen Activation

  Zymogen activation is a crucial regulatory mechanism in various biological processes, particularly in the context of proteolytic enzymes. Zymogens are inactive precursor forms of enzymes that require specific activation steps to become catalytically active. This process often involves the removal of an inhibitory domain or the exposure of the active site through proteolytic cleavage. Zymogen activation is a tightly regulated process that helps prevent the premature or uncontrolled activity of potent enzymes, which could otherwise lead to undesirable consequences. The activation of zymogens is often triggered by specific stimuli, such as changes in pH, the presence of cofactors, or the action of other proteases. This mechanism is particularly important in physiological processes like blood coagulation, digestion, and immune response, where the controlled activation of enzymes is crucial for maintaining homeostasis and preventing tissue damage. Understanding the molecular mechanisms and regulation of zymogen activation is an active area of research, as it provides insights into the complex regulatory networks that govern various biological systems and holds potential for the development of targeted therapies for diseases associated with dysregulated proteolytic activity.