Catalase

CATALASE, the name given by Loew in 1901 to the enzyme that decomposes H₂O₂ into water and molecular oxygen. The existence of an organic catalyst capable of decomposing H₂O₂ was already known to Thenard, who in 1818 reported that particles of various animal tissues, like noble metals, are capable of decomposing H₂O₂. In 1898, Raundnitz succeeded in separating in milk the ability to decompose H₂O₂ from the ability to produce bluing of guaiac resin, and finally in 1901 Loew isolated from an extract of tobacco leaves the enzyme that decomposes H₂O₂ and named it catalase. The individuality of catalase was soon established by other authors. Its distinction from peroxidase, with which it continued to be confused, was established by the works of Bach and Chodat. A tremendous number of works have appeared on the subject of catalase. The content of catalase in human blood was studied for diagnostic purposes (especially numerous are the studies by Burge). In view of the inadequacy of the methodology used by the authors, their data must be treated skeptically. Preparation of catalase. Any animal or plant tissue can serve as the starting material for preparing catalase, since catalase is contained in all cells of aerobic organisms, but in practice those tissues or organs are used that contain particularly significant amounts of catalase, such as the liver of horses, cattle, and sheep. The simplest method for preparing highly active preparations is the method of Batelli and Stern: extraction with 2-3 volumes of water of finely minced liver, precipitation of the resulting extract with 2 volumes of ethyl alcohol, secondary extraction of the resulting precipitate with water, filtration, and secondary precipitation of the filtrate with 2 volumes of ethyl alcohol. The precipitate dried at room temperature shows great activity: 1 g of this powder can decompose in 5 minutes at room temperature about 3 kg of pure H₂O₂, releasing about 1,000 liters of O₂. Catalase preparations prepared by this method (hepatocatalase of Batelli and Stern) retain full activity for many years (more than 20 years). Significant purification of these preparations from substances accompanying catalase is achieved by adsorption with kaolin or with a mixture of Na₂HPO₄ + CaCl₂ by the method used by Hennichs. Properties of catalase. The chemical composition of catalase is as little known as the chemical composition of other enzymes. In the ash of the purest catalase preparations, 3.3-4.1% iron is found. The action of catalase is strictly specific: it is limited to the decomposition of H₂O₂. The stability of catalase with respect to high temperature is not the same for different preparations. Catalase from cold-blooded animals is more sensitive to high temperature than catalase from warm-blooded animals. In dry form, catalase is very heat-resistant. Proteolytic enzymes (trypsin and erepsin) destroy catalase, pepsin has no effect. Catalase is completely harmless to the bodies of higher animals. The influence of various physical and chemical factors on the action of catalase. It is necessary to distinguish the action of these factors on the enzyme itself and their influence on the course of the reaction. What is noted as a stimulating or retarding action is in essence the algebraic sum of these two factors. Among the inactivating substances, antienzyme occupies a special place; this substance was found by Batelli and Stern in the blood and various tissues of animals; in the presence of O₂ or a hydrogen acceptor, even at room temperature, solutions of catalase under the influence of antienzyme quite rapidly lose their activity. Equilibrium is reached when ²/₃ of all catalase is inactivated. Catalase inactivated by antienzyme is easily restored by philocatalase. Methyl and ethyl alcohols, aldehyde, etc., act similarly to philocatalase to some extent. These same substances protect catalase from the inactivating action of antienzyme. The apparent activation of catalase by various tissue extracts is nothing other than the restoration, or regeneration, of catalase inactivated by antienzyme. Optimal reaction conditions. Between 10° and 50° the reaction rate does not change. As for the concentration of hydrogen ions, no significant difference is noted within the range from pH=5.0 to pH=8.0. At pH8.0, retardation is observed. Methods for determining catalase. The only reaction of catalase is the decomposition of H₂O₂ into water and molecular oxygen, and therefore the activity of this enzyme can be measured either by titrating the residual, undecomposed H₂O₂ or by measuring the released molecular oxygen. To determine the content of catalase in tissues and body fluids, the following method is used: the tissue under study is finely minced, extracted for 30 minutes at low temperature with several volumes of water containing a small amount of ethyl alcohol (0.02%) to protect catalase from the antienzyme accompanying it in the tissues. The resulting extract is diluted with water (containing 0.02% ethyl alcohol) so that 1 volume of this solution, added to 1 volume of 1% H₂O₂, decomposes in 5 minutes and at room temperature approximately half of the added H₂O₂. Completely pure H₂O₂ (pH=6.5-7.0) is used. Apparatus for determining catalase by the method of Batelli and Stern (see figure). An Erlenmeyer flask (A) with a capacity of 100 cm³, into which the catalase solution under study is placed, is connected with a burette (B), from which a certain amount of H₂O₂ solution is introduced into the flask, and with a precisely graduated eudiometer (C), into which the oxygen released during the decomposition of H₂O₂ passes. The pear-shaped funnel (D) serves for displacing air from the eudiometer and for setting the level. The results obtained by this method are significantly more accurate than the data previously given regarding the content of catalase in tissues and blood, since previous authors completely overlooked the existence of antienzyme. Distribution of catalase. There are significant variations in the content of catalase in the cells and tissues of individuals of the same species of animal; nevertheless, some constancy is observed among members of the same family, especially of the same litter. The regularities in the distribution of catalase in different organs could not be established to this day, but in general it is noted that glands are much richer in catalase than the brain and muscles. One cannot judge the content of catalase in the entire organism on the basis of determining catalase in only the blood, as is often practiced, especially in the clinic. The content of catalase in plants and its distribution in different plant organs has been studied relatively little. Bach and Oparin establish a connection between the aerobic germination of seeds and an increase in their catalase content. The maximum is reached here after 3-6 days. Catalase of bacteria has been studied in more detail. It has been established that anaerobic bacteria are completely devoid of catalase; in aerobic bacteria, significant variations in catalase content are noted not only in different species, but also in cultures of the same species. The role and physiological significance of catalase have not yet been clarified. Of the hypotheses put forward by various authors, none has proven entirely satisfactory. Given the wide distribution of this enzyme, it can be assumed that it plays an important role in the general chemistry of the cell and, in view of the parallelism between the presence of this enzyme and the oxybiosis of the organism, it is also logical to assume that it must have a significant role precisely in oxidative processes. However, there is no parallelism between the intensity of energy-supplying oxidative processes and the amount of catalase in different organs and in different species of animals. According to Stern's data, there is a close connection between catalase (or rather the catalase system) and the type of oxidative processes: catalase abounds in those tissues (kidney, liver, etc.) where oxidases (typical oxidative enzymes) are present, which play a predominantly protective role in higher organisms; catalase is almost absent in those tissues (brain, muscle) where the oxidative catalysts are almost exclusively oxidones, playing a significant role in the respiratory energy metabolism.

L. Stern.

Catalase, catalepsy (from Greek katalepsis - seizure), the freezing of the body and its individual members in externally imposed positions, combined with the loss of the ability to make voluntary movements. C. is a phenomenon very often observed in persons in a hypnotic sleep. The appearance of symptoms of C. serves as one of the earliest objective signs of hypnosis; the hypnotist raises the patient's arm, and in the case of sleep occurring, it hangs in the air. In different individuals, phenomena of such suggestive C. are induced to varying degrees: in some it cannot be obtained at all, in others any part of the body can freeze cataleptically in any position. Phenomena of C. arise most easily in the upper extremities, while the legs retain their given position to a lesser degree and for a shorter time than the arms; it is even more difficult to induce C. in the muscles of the torso. Sometimes the freezing is incomplete and relative, so that the members somewhat change their position, and a raised arm, for example, first lowers somewhat, and then freezes. The degree of muscular tension in suggestive C. can also vary individually. Bernheim distinguished three types of catalepsy: flaccid C., waxy flexibility (flexibilitas cerea), and tetanic C. In the first form, the limb only approximately retains its given position, and a small push is sufficient to move it from that position; in the second, the body parts turn out to be so plastic that they freeze exactly in the poses given to them, immediately changing them in accordance with the movements made by the hypnotist; finally, in the third, moving the frozen limb from the position it has taken is possible only after significant effort, and sometimes the muscles freeze in such a state of tension that, for example, the patient's body can be held stretched in the air between two chairs placed apart. However, such differentiation of degrees of C. is artificial and is based not on the actual features of different hypnotic states, but on the greater or lesser training of the patients. The duration of C. depends on the muscular strength and degree of fatigue of the patient, averaging 5-10 minutes; with significant fatigue, the patient's body parts relax and fall, obeying the force of gravity. In some cases (in hysterics, persons in a state of severe exhaustion), the phenomena of C. arise extraordinarily easily; Lasegue succeeded in inducing them simply by closing the patient's eyes; cases of their appearance in waking subjects have also been described. Suggestive C. is always a direct result of direct or indirect suggestion (or autosuggestion) and has nothing to do with physical changes in the muscles: its basis is the unconscious tendency of the patient to maintain that ratio of contraction and tonic tension of various muscles that would provide the patient with sensations and position (skin, muscle, and joint senses) identical with those that originally arose. In addition to suggestive C., phenomena of freezing of the body and its parts also occur in lethargic encephalitis, some infectious diseases, poisonings, in diseases of the cerebellum and its pathways, etc.; however, the mechanism of their origin here is different, namely, organic or functional disorder of the activity of the subcortical motor centers. C. is an essential component of the symptom complex of catatonia (see).