Enzyme systems in articular cartilage

Abstract

An attempt was made to study in detail enzyme systems in cartilage concerned with glycolysis and other oxido-reductions. Cartilage from young normal animals (calf) was used in the form of slices or extracts. For comparison some expts. were carried out with other joint tissues, synovial fluid, synovial membrane and ligaments. Adeno-sinetriphosphoric, muscle adenylic, yeast adenylic and ino-sinic acids and adenosine were attacked in cartilage by dephosphorylation and/or deamination. Hypoxanthine was the end-product of these reactions. Cozymase and Warburg''s coenzyme lost their catalytic activities after prolonged incubation with cartilage. Cocarboxylase also was unstable under the influence of cartilage. The ability of cartilage to produce lactic acid from various phosphorylated and non-phosphorylated carbohydrates was tested. The small positive results obtained with some of the substances investigated suggested 2 mechanisms of lactic acid production in cartilage, one of which depended upon the presence of cozymase while the other was catalysed by glyoxalase. As intermediary products methyglyoxal was formed from hexosediphosphoric acid and pyruvic acid from phospho-glyceric acid. Articular cartilage was almost completely unable to oxidize substances such as succinate, lactate, aldehyde and several other substances which were rapidly oxidized in other tissues.