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Common G102S polymorphism in chitotriosidase differentially affects activity towards 4‐methylumbelliferyl substrates
Author(s) -
Bussink Anton P.,
Verhoek Marri,
Vreede Jocelyne,
Ghauharalivan der Vlugt Karen,
DonkerKoopman Wilma E.,
Sprenger Richard R.,
Hollak Carla E.,
Aerts Johannes M. F. G.,
Boot Rolf G.
Publication year - 2009
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2009.07259.x
Subject(s) - substrate (aquarium) , recombinant dna , allele , chitinase , polymorphism (computer science) , chemistry , biochemistry , biology , enzyme , gene , ecology
Chitotriosidase (CHIT1) is a chitinase that is secreted by activated macrophages. Plasma chitotriosidase activity reflects the presence of lipid‐laden macrophages in patients with Gaucher disease. CHIT1 activity can be conveniently measured using fluorogenic 4‐methylumbelliferyl (4MU)–chitotrioside or 4MU–chitobioside as the substrate, however, nonsaturating concentrations have to be used because of apparent substrate inhibition. Saturating substrate concentrations can, however, be used with the newly designed substrate 4MU–deoxychitobioside. We studied the impact of a known polymorphism, G102S, on the catalytic properties of CHIT1. The G102S allele was found to be common in type I Gaucher disease patients in the Netherlands (∼ 24% of alleles). The catalytic efficiency of recombinant Ser102 CHIT1 was ∼ 70% that of wild‐type Gly102 CHIT1 when measured with 4MU–chitotrioside at a nonsaturating concentration. However, the activity was normal with 4MU–deoxychitobioside as the substrate at saturating concentrations, consistent with predictions from molecular dynamics simulations. In conclusion, interpretation of CHIT1 activity measurements with 4MU–chitotrioside with respect to CHIT1 protein concentrations depends on the presence of Ser102 CHIT1 in an individual, complicating estimation of the body burden of storage macrophages. Use of the superior 4MU–deoxychitobioside substrate avoids such complications because activity towards this substrate under saturating conditions is not affected by the G102S substitution.