Action of neuraminidase on haptoglobulin.

Abstract

IN the course of work on the chemical structure of haptoglobin (Hp)1, we have had occasion to investigate the action of neuraminidase on the Hp and on the complex of Hp with haemoglobin (Hb-Hp). The neuraminidase employed was prepared as described by Mayron and Rafelson2,3 from influenza virus, Asian strain (Jap. 305), and is free of proteolytic activity and glucosidase activities other than neuraminidase action. The Hp II preparations utilized were prepared as previously described4, and are considered to approach the stage of theoretical purity. Such preparations contain 5.1 ± 0.1 per cent N-acetylneuraminic acid (NANA)1. The liberation of NANA from Hp II and Hb-Hp II was determined by the method of Warren5 using three-times crystallized NANA as a standard. A typical enzyme incubation at 37° employed 2–5 mgm. of Hp II or Hb-Hp II and 0.1 to 0.3 unit of neuraminidase in 0.1 M phosphate buffer, pH. 6.5, total volume 2–3 ml. One unit of enzyme activity is defined as that amount of enzyme which liberates 1 mgm. of NANA from an excess of neuramin-lactose in 1 hr. at 37°, pH. 6.5.