Biochemical properties of h-glucosidase in leukocytes from patients and obligated heterozygotes for Gaucher disease carriers Kristiane Michelin a,b , Alessandro Wajner a,b , Hugo Bock a ,A ˆ ngela Fachel a , Roberto Rosenberg c , Ricardo Flores Pires a , Maria Luiza Saraiva Pereira a,b , Roberto Giugliani a,d , Janice Carneiro Coelho a,b, * a Medical Genetics Service, Hospital de Clı ´nicas de Porto Alegre, Porto Alegre, RS, Brazil b Department of Biochemistry, ICBS, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil c Department of Genetics, IB, Universidade de Sa ˜o Paulo, Sa ˜o Paulo, SP, Brazil d Departament of Genetics, IB, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil Received 11 February 2005; received in revised form 1 June 2005; accepted 1 June 2005 Available online 22 July 2005 Abstract Background: Gaucher’s disease (GD) is a disorder caused by the deficiency of lysosomal h-glucosidase, an enzyme that participates in the degradation of glycosphingolipids. Deficiency of this enzyme results in the storage of glucocerebrosides in lysosomes of macrophage. No studies are available in the literature comparing biochemical and kinetic behavior of this enzyme in leukocytes and fibroblasts from normal individuals, obligate heterozygotes and patients with GD. Methods: The behavior of h-glu in terms of optimum pH, heat stability, Km and Vmax in leukocytes from patients with GD and obligated heterozygotes with different genotypes and normal individuals were characterized. Results: Optimum pH was similar in all groups analyzed. In terms of Km and Vmax, several differences among heterozygotes and homozygotes groups and among these groups and normal enzyme were observed. Enzyme from all groups were inactivated when preincubated at 60 8C, but some enzymes were more stable than other. Results showed a different behavior of the enzyme in the 3 groups under analysis. Such behavior varied according to individual mutation. Conclusions: The catalytic gradient presented by h-glu allowed the correlation of N370S mutation–which presented more stable biochemical properties–with the non-neurological clinical condition of the disease and the catalytically less stable mutation (D409H), with the neurological clinical condition of GD. This study contributes to a better understanding of the repercussion of the different mutations on the protein function, thus allowing to predict the severity of such complex metabolic disorder and to anticipate the most appropriate intervention for each case specifically. D 2005 Elsevier B.V. All rights reserved. Keywords: Gaucher’s disease; h-Glucosidase; Lysosomal storage diseases; Sphingolipidosis 0009-8981/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cccn.2005.06.010 * Corresponding author. Servic ¸o de Gene ´tica Me ´dica, Hospital de Clı ´nicas de Porto Alegre, Rua Ramiro Barcelos, 2350, Porto Alegre-RS, 90035-903, Brazil. Tel.: +55 51 2101 8011; fax: +55 51 2101 8010. E-mail address: jcoelho@hcpa.ufrgs.br (J.C. Coelho). Clinica Chimica Acta 362 (2005) 101 – 109 www.elsevier.com/locate/clinchim