Catalase

• OMIM: 115500
• UniProt: P04040

Catalase (gene name: CAT) is an enzyme that hydrogen peroxide ( H2O2) to oxygen (O2 ) and water ( H2O) are reacted. Hydrogen peroxide formed during the degradation of hyperoxides by superoxide dismutase. It is a byproduct of the breakdown of purines and in the oxidation of fatty acids and can cause damage to the genome and proteins. Catalases are therefore in almost all aerobically living organisms in humans is primarily in the peroxisomes of the liver and kidneys, and erythrocytes. Mutations in the CAT gene can lead to hereditary Katalasemangel, which occurs frequently in Japan.

System

Based on sequence and structure catalases are divided into three classes.

• Monofunctional heme -containing enzymes
• Bifunctional heme -containing catalase - peroxidases
• Manganese-containing enzymes ( without heme group )

The human catalase (PDB 1DGF ) consists of four identical subunits of 60 kDa. Thereof each containing a heme group and a NADPH binding site.

Catalyzed reaction

The reaction takes place in two steps. In the first step, hydrogen peroxide is reduced and the enzyme is oxidized, the product water is produced.

In the second step, hydrogen peroxide and the enzyme is reduced and oxidized, and thus the oxygen is released as a product of addition to a further water molecule.

The total equation is:

Both turnover number and catalytic efficiency of the enzyme are among the highest ever found in enzymes values ​​(Table ).

At low concentrations of hydrogen peroxide can be oxidized via the aldehyde to the acid by the oxidized catalase methanol and ethanol.

Laboratory use

In microbiology, the catalase test is used to differentiate bacteria. Clinically significant is particularly the differentiation of catalase -positive staphylococci of catalase -negative streptococci. In this case, a drop of catalase reagent ( 3- percent hydrogen peroxide solution ) is added to a microscope slide and a loop material into bacteria kept short. Positive reaction: Direct bubbling, blistering; Negative reaction: no or delayed effervescence. Alternatively, dilute hydrogen peroxide are dripped directly onto a bacterial colony on an agar plate.

Most aerobic and facultative anaerobic bacteria such as fungi have the enzyme catalase, which is able to cleave the toxic for the cells H2O2.

Experimental Hydrogen peroxide is used in biology for inducing programmed cell death of the isolated eukaryotic cells.