Matrix metalloproteinase-9 in a unique proteoglycan form in avian embryonic growth plate cartilage

The appearance of a high molecular weight gelatinolytic enzyme (230 kDa) correlated with cartilage collagen loss in chick embryonic tibias cultured with lipopolysaccharide. This 230 kDa enzyme was purified and its activity was measured on synthetic and natural substrates. The enzyme was activated by aminophenylmercuric acetate and inhibited by ethylenediaminetetraacetic acid, phenanthroline, marimastat or tissue inhibitors of metalloproteinases. Amino acid sequences of peptides derived from the purified enzyme showed identity with avian MMP-9. Digestion of the intact enzyme with chondroitinase decreased the size of the molecule to 80 kDa on SDS–PAGE. When chick embryonic tibia cultures were radiolabeled with 35S-sulfate, the radiolabel co-purified with the 230 kDa gelatinase. Chondroitinase treated 230 kDa gelatinase also reacted with specific anti-chondroitin sulfate antibodies and FACE analysis revealed a predominance of chondroitin-4-sulfate. These results demonstrate this avian matrix metalloproteinase contained glycosaminoglycan chains. To our knowledge, this is the first report of a matrix metalloproteinase in a proteoglycan form.