The intracellular proteases (IP) of the cellular extract of Thermoactinomyces vulgaris are characterized as to the biochemical properties compared with the corresponding extracellular proteases (EP). According to that, the storage stability and the temperature and pH behaviour (optimum, stability) of both of the proteases are identical. Nevertheless, differences were detected between IP and EP after the action of several effectors and different substrates. As could be seen after a column chromatographic separation of the IP of the cellular extract, it is composed of at least 3 proteases, two of them are serine proteases which can be inhibited moreover unspecifically by p-chloromercuri benzoate. The purified proteases (IP) are very instable and therefore not yet characterized in detail.

The investigation concerning the localization of proteolytically active enzymes in the cells of Thermoactinomyces vulgaris show that the enzymes are present in a dissolved form in the cellular extract (75%) as well as linked to the solid cell components (25%). The ratio of the activities of the soluble periplasmatical fraction to the soluble cytoplasmatical fraction to the insoluble cytoplasmatical membrane fraction was found to be 2:1:1. The formation of the proteins during the cultivation is measured by detecting the activity in the cellular extract. As soon as enough of biomass is present (weighable) in the medium, the protease activity can be detected in the cellular extract. It increases during the fermentation and amounts to 1 to 2% of the activity of the proteases in the medium between the 10th and the 24th hour. A correlation between the formation of biomass and enzymes does not exist.

Anhand eines Literaturiiberblickes mird der gegenwartige Stand der Kenntnisse iiber den Kasefehler ,,bitter" sowie iiber Bildung, Abbau und Struktur von bitteren Peptiden aus Casein dargelegt.

The cleavage specificity of a protease from Thermoactinomyces vulgaris (thermitase) was determined by the insulin B-chain and the cleavability of casein and haemoglobin by this enzyme as compared to other proteases (trypsin, chymotrypsin, proteases from Bac. megaterium and cytophages). The most intense splitting effect on the substrates under investigation (insulin B-chain, casein and haemoglobin) is exerted by thermitase, i. e., the unspecificity of this enzyme is especially marked.

Es werden bittere Peptide aus bitterem Käse und aus enzymatischen Caseinhydrolysaten isoliert und mit Hilfe chromatographischer Verfahren rein dargestellt. Die geprüften Proteasen verschiedenen Ursprungs sind alle in der Lage, aus Casein bittere Komponenten zu bilden. Die Intensität der Bitterstoffbildung ist unterschiedlich und korreliert nicht mit der Stärke der allgemeinen Caseinproteolyse.