User:Majiang21/Carbonic anhydrase

First 250 Words Contribution (Revised)

Subtopics:

• Introduction section: Improve the structure of the paragraph and create a new “occurrence and function” section.
• Mechanism section: Discuss the mechanism in sufficient detail and explain the structure-function principles, including the His-64 proton shuttle.
• Carbon capture and sequestration section: Give more explanation, including the flue gas scrubbing diagram.

Type of contributions:

• Add new content (occurrence and function section) and edit the existing materials for the contributions.

Bolded sentences were copied from the original article.

Carbonic Anhydrase

Introduction

Remove and re-write the third paragraph

Carbonic anhydrase is critical to hemoglobin function via the Bohr effect which catalyzes the hydration of carbon dioxide to form carbonic acid and rapidly dissociate into water.

Occurrence and function

Carbonic anhydrase was initially found in the red blood cells of cows in 1933 and was simultaneously discovered by Rougton in Cambridge and Meldrum in Philadelphia who were searching for a catalytic factor.

Regulation of pH

Carbonic anhydrase plays an essential role in regulating the blood pH, which speeds up the CO₂ + H₂O ${\ce {<=>}}$ HCO₃^-+ H⁺ reaction to ensure the equilibrium balance is rapidly maintained. The equilibrium reaction is influenced by the proportion of bicarbonate and H⁺ to carbon dioxide. The HCO₃^- is a conjugate base that neutralizes acids, and the H⁺ is a conjugate acid that neutralizes bases by Acid-base homeostasis. The HCO₃^- and H⁺ are ideal for buffering pH in the blood and tissues because the pKa is close to the physiological pH = 7.2 – 7.6. Since HCO₃^- and H⁺ are regulated in the kidneys and plasma carbon dioxide is regulated in the lungs, both actions in the kidneys and lungs are important to maintain the stability of blood pH. Therefore, carbonic anhydrase helps with the H+ secretion into the lumen of the kidney renal tubule and the reabsorption of HCO₃^- in the kidneys. Also, it helps the carbon dioxide transport from the lung tissue to the alveoli in the pulmonary capillary, where the carbon dioxide will be excreted during exhalation.

Carbonic anhydrase is a very ancient enzyme found in both domains of prokaryotes that exists in six different classes among most of the living organisms. These families are not similar in sequence or structure because they evolved independently of each other, but all evolved the same Zn²⁺ active site structure, showing a great example of convergent evolution.

Figures Contribution (250 word equivalents)

Contributions: Structure section (carbonic anhydrase)

• Replace student "CAII Enzyme Whole" figure
• Replace student "Zoom in of Active site of CAII..." figure

CAII enzyme (PDB code: 1CA2) showing the secondary structures and the hydrophobic pocket (right side of the Zn²⁺) formed by the beta sheet (blue) and the two valine and one tryptophan side chains

Active site of CAII enzyme (PDB code: 1CA2) which O = red, N = blue, Zn = grey and C = green