N-acetyl-beta-D-hexosaminidase system in synovial fluid.

The present study was undertaken with the object of examining the N-Acetyl-beta-D-hexosaminidase activity in joint effusions from non-inflammatory (osteoarthrosis) and inflammatory (rheumatoid arthritis, gouty arthritis and chondrocalcinosis) joint diseases. The biochemical properties of four purified molecular forms were investigated. They were separated on the basis of their net charge, using DEAE-cellulose anion-exchangers. In the order of their outcome from the anion exchanger the four enzymes (B, I1, I2 and A) were found to have pH optima at 4.5-4.75, 4.20, 4.00 and 4.75, respectively. The first three enzymes proved to be heat-stable and the fourth enzyme fraction was a heat-labile form. By means of gel-filtration techniques, the enzymes were eluted into two fractions. The first contained the thermolabile A form and the molecular weight of this enzyme was estimated at 162000. The second fraction included the three thermostable enzymes. Their molecular weight was estimated at 135000. As described by Ikonne & Ellis (6) the hexosaminidase A from sera was less tightly held by the anion-exchanger than was the hexosaminidase A from tissues (polymorphonuclear cells, synovial membrane tissue, cartilage). Thus the serum type (As) must be distinct from the tissue type (At). The activity of the tissue type probably originating from the leukocytes and from the synovial membrane was more pronounced in the synovial effusions of the patients with inflammatory joint diseases. The hexosaminidase A fraction from synovial fluids of patients with osteoarthrosis contained only the serum type of enzyme.