Enzyme Activities in Chick Embryonic Cartilage

Abstract

Some characteristic enzymatic activities were determined in chick embryonic cartilage and compared with the analogous activities in bone and liver. Chondrocytes were isolated, broken by sonication, and subjected to subcellular fractionation to yield a nuclear pellet, the mitochondrial, lysosomal, and microsomal fractions, and the high speed supernatant solution. It was established that these fractions are characterized by enzymatic activities usually associated with similar fractions in other tissues, but with some quantitative differences. Lysozyme, a particulate-associated enzyme in other tissues, was not detected in any subcellular fraction even by the sensitive technique of microzone electrophoresis and is therefore considered to be primarily extracellular in cartilage.

Lysozyme in Epiphyseal Cartilage

“…This suggests that one function of lysozyme at these sites may be to interact with polysaccharides or other anions, such as glycoproteins, thus altering their reactivity with calcium and perhaps other ions in a manner promoting calcification . In the accompanying communication (33), in which a detailed biochemical analysis of the isolated chondrocytes is described, it will be pointed out that in cartilage, unlike some other tissues, lysozyme is not a lysosomal enzyme, nor is it a detectable part of any other cytoplasmic particulate fraction . The immunocytochemical studies also point out that, even in cartilage matrix, lysozyme is heterogeneously distributed since the immunologic markers were particularly concentrated in the area corresponding to the chondrocyte lacunae .…”