Human articular cartilage secretes characteristic metal dependent proteinases upon stimulation by mononuclear cell factor.

Human articular cartilage stimulated during organ culture by the addition of human blood mononuclear cell factor concomitantly released latent proteinases and proteoglycan. Gel chromatography at pH 7.4 separated 2 distinct latent enzymes: a general proteinase which could degrade proteoglycan, casein and gelatin, and a collagenolytic activity of smaller molecular size. The general proteinase was calcium dependent and could be activated by either trypsin or 4-aminophenylmercuric acetate; the former procedure invariably generating greatest activity. The enzyme exhibited a broad bimodal pH profile against proteoglycan, with optimum activity at pH 5.5.