Prolonged hyperlipasemia attributable to a novel type of macrolipase

Abstract

Background: We present the case of an 80-year-old woman who was admitted to hospital with an intermittent volvulus of the right colon. A total colectomy was performed. Initially, serum amylase and lipase increased concordantly, but after a few weeks amylase normalized (85 U/L), whereas lipase increased to 3764 U/L. This discrepancy and persistence of hyperlipasemia suggested a macromolecular form of lipase. Methods: The nature of the macromolecular complex was studied using high-pressure liquid gel-permeation chromatography, affinity chromatography, (immuno) electrophoresis, and immunodiffusion. Results: Gel-permeation chromatography revealed a macrolipase, with a molecular mass >900 kDa, that contributed up to 56% of total serum lipase activity. Butanol extraction of the specimen did not alter the elution profile. The thermostabilities of pancreatic lipase and the macroform were similar, whereas activation energy (E(a)) was lower in the macromolecular lipase (28 ± 4 kJ · mol-1 · K-1 vs 48 ± 7 kJ · mol-1 · K-1 (P = 0.02). Agarose electrophoresis showed a broad band of lipase activity at the application site. Protein A-Sepharose affinity gel chromatography excluded IgG-linked lipase. Agarose electrophoresis and immunofixation excluded linkage to other immunoglobulins. Radial immunodiffusion did not show lipase activity in the immunoglobulin precipitation bands. Radial immuno-diffusion with α2-macroglobulin (α2-MG) antibodies showed a diffuse spot of lipase activity within the precipitation band, suggesting a macromolecular association between lipase and α2-MG. Affinity gel chromatography against α2-MG showed lipase activity in the α2-MG-bound fractions. Conclusion: This is the first report of a macrolipase in which an association between α2-MG and lipase is described. (C) 2000 American Association for Clinical Chemistry.