Related Experiment Video
Updated: Jun 19, 2026
07:26
Site Specific Lysine Acetylation of Histones for Nucleosome Reconstitution using Genetic Code Expansion in Escherichia coli
Published on: December 26, 2020
TISSUE-DIGESTING ENZYME (HISTASE) OF STREPTOCOCCI
1Department of Pathology and Bacteriology of the Johns Hopkins University, Baltimore.
The Journal of Experimental Medicine
|October 30, 2009
Summary
A novel proteolytic enzyme, named histase, has been identified in hemolytic streptococci. This enzyme effectively digests animal tissues, similar to trypsin, but shows no correlation with hemolysis.
Area of Science:
- Microbiology
- Enzymology
- Biochemistry
Background:
- Hemolytic streptococci are known to produce various extracellular enzymes.
- The presence and activity of proteolytic enzymes in these bacteria have not been fully characterized.
Purpose of the Study:
- To identify and characterize a novel extracellular proteolytic enzyme in beta-hemolytic streptococci.
- To investigate the enzyme's activity on animal tissues and its relationship with hemolytic activity.
Main Methods:
- Culturing of over 30 strains of beta-hemolytic streptococci in cooked meat medium.
- Analysis of sterile filtrates for proteolytic activity and enzyme properties.
- Incubation of cooked meat cultures at different temperatures and time points.
- Assessment of tissue digestion and correlation with hemolysis.
Main Results:
- An extracellular proteolytic enzyme, proposed name histase, was found in over 30 strains.
- Histase partially digested cooked meat, with 50-75% digestion observed over 3 weeks.
- No correlation was found between hemolytic activity and proteolysis.
- The enzyme showed similar activity to trypsin and digested both beef and human tissues.
Conclusions:
- Hemolytic streptococci produce a heat-sensitive proteolytic enzyme, histase.
- Histase is capable of digesting animal tissues, independent of hemolytic activity.
- The enzyme's characteristics suggest a significant role in bacterial tissue degradation.
Related Concept Videos
01:02Protein Digestion
Protein digestion begins in the stomach, where the highly acidic environment can easily disrupt protein structure by exposing the peptide bonds of polypeptide chains. After polypeptide chains are broken into individual amino acids by a series of digestive enzymes, the amino acids are transported to the liver via the bloodstream to produce energy.
01:20Determinants of Bacterial Pathogenicity and Virulence
Pathogenic bacteria employ a variety of strategies to establish infections, including the secretion of extracellular enzymes that act as potent virulence factors. These enzymes facilitate bacterial colonization of host tissues and help evade immune surveillance. By targeting structural components of host tissues and interfering with immune mechanisms, these enzymes play a pivotal role in disease progression.Extracellular Enzymes Facilitating Tissue Invasion: Several bacterial pathogens secrete...
01:06Lipid Digestion
Lipids are large molecules that are generally not water-soluble. Since most of the digestive enzymes in the human body are water-based, there are specific steps the body must take to break down lipids and make them available for use.
01:26Stomach Histology
The stomach comprises several layers that work together to facilitate digestion and protect the organ. The outermost layer is called the serosa, which provides support and protection to the stomach. The muscularis externa layer is responsible for the mechanical breakdown of food by contracting and moving the stomach. The submucosa layer, located beneath the muscularis externa, contains connective tissue, blood vessels, nerves, and glands that secrete mucus and other substances essential for...
02:32Histone Modification
The histone proteins have a flexible N-terminal tail extending out from the nucleosome. These histone tails are often subjected to post-translational modifications such as acetylation, methylation, phosphorylation, and ubiquitination. Particular combinations of these modifications form “histone codes” that influence the chromatin folding and tissue-specific gene expression.
Acetylation
The enzyme histone acetyltransferase adds acetyl group to the histones. Another enzyme, histone deacetylase,...
Acetylation
The enzyme histone acetyltransferase adds acetyl group to the histones. Another enzyme, histone deacetylase,...
01:30Bacterial Phylum Actinobacteria
Coryneform bacteria are gram-positive, aerobic, nonmotile rods that exhibit irregular, club-shaped, or V-shaped arrangements. Their V-shape results from snapping division, where the inner cell wall layer forms the cross-wall, while the outer layer remains intact until it ruptures on one side, causing the daughter cells to bend away.The primary genera are Corynebacterium and Arthrobacter. Corynebacterium includes diverse species, ranging from saprophytes to pathogens like Corynebacterium...