Related Experiment Video
Updated: Jun 19, 2026
09:52
Optimizing the Growth of Endothiapepsin Crystals for Serial Crystallography Experiments
Published on: February 4, 2021
CRYSTALLIZATION OF PEPSIN FROM ALCOHOL
1Laboratories of The Rockefeller Institute for Medical Research, Princeton, New Jersey.
The Journal of General Physiology
|October 30, 2009
Summary
Pepsin crystallization is achievable using alcohol, yielding distinct crystal forms. This enzyme exhibits stability in specific alcohol concentrations and pH levels, with no enhanced activity observed after hydrogen peroxide treatment.
Area of Science:
- Biochemistry
- Enzymology
Background:
- Pepsin is a key digestive enzyme.
- Understanding pepsin's properties is crucial for biochemical research.
Purpose of the Study:
- To investigate the solubility and crystallization of pepsin.
- To determine the stability of pepsin in various alcohol concentrations and pH conditions.
- To assess the effect of hydrogen peroxide on pepsin activity.
Main Methods:
- Pepsin solubility and crystallization were studied using different alcohol concentrations.
- Enzyme stability was tested at various pH levels and alcohol concentrations.
- Proteolytic activity was assessed before and after hydrogen peroxide treatment.
Main Results:
- Pepsin is soluble in 65% alcohol and crystallizes from 20% alcohol, forming needles, plates, or hexagonal bipyramids.
- Pepsin is stable in 20% alcohol at pH 2.0 but inactivated by higher concentrations.
- Pepsin remains stable in 65% alcohol at pH 4.0-5.0 but is rapidly inactivated in more acidic conditions.
- Hydrogen peroxide treatment did not increase pepsin activity.
Conclusions:
- Pepsin can exist in different crystalline forms.
- Pepsin's stability is dependent on alcohol concentration and pH.
- Hydrogen peroxide does not enhance pepsin's proteolytic activity.
Related Concept Videos
01:12Acid Halides to Esters: Alcoholysis
Alcoholysis is a nucleophilic acyl substitution reaction in which an alcohol functions as a nucleophile. Acid halides react with alcohol to produce esters. The mechanism proceeds in three steps:
01:27Production of Alcohol
Continuous fermentation is a key strategy in industrial ethanol production, particularly when efficiency, scalability, and high yields are essential. This approach allows for uninterrupted operation and optimized resource utilization. The primary feedstock, corn starch, undergoes enzymatic hydrolysis facilitated by α-amylase and glucoamylase. These enzymes break down the starch into fermentable sugars such as glucose, which are readily assimilated by fermentative microorganisms.Fermentation...
01:20Carboxylic Acids to Esters: Acid-Catalyzed (Fischer) Esterification Overview
The Fischer esterification reaction was developed by the German chemist Emil Fischer in 1895. It is a condensation reaction between carboxylic acids and alcohols in an acidic medium to give esters and water.
01:19Aldehydes and Ketones with Alcohols: Hemiacetal Formation
Similar to water, alcohols can add to the carbonyl carbon of the aldehydes and ketones. The addition of one molecule of alcohol to the carbonyl compound forms the hemiacetal or half acetal. As depicted below, in a hemiacetal, the carbon is directly linked to an OH and OR group.
02:35Acid-Catalyzed Dehydration of Alcohols to Alkenes
In a dehydration reaction, a hydroxyl group in an alcohol is eliminated along with the hydrogen from an adjacent carbon. Here, the products are an alkene and a molecule of water. Dehydration of alcohols is generally achieved by heating in the presence of an acid catalyst. While the dehydration of primary alcohols requires high temperatures and acid concentrations, secondary and tertiary alcohols can lose a water molecule under relatively mild conditions.
01:08Esters to β-Ketoesters: Claisen Condensation Mechanism
Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the presence of an alkoxide base. The reaction commences with the deprotonation of the acidic α hydrogen by the base to form a resonance stabilized ester enolate. This nucleophilic ion then attacks the carbonyl center of another ester molecule to generate a tetrahedral alkoxide intermediate. Next, the expulsion of the alkoxide group from the intermediate restores...