[Alpha-L-fucosidase of normal and pathological blood cells]

The glycosidases, enzymes which participate in the degradation of glycoproteins and glycolipids inside the lysosomes are themselves glycoproteins and, for one enzyme, several forms may be isolated in tissues and in biological fluids, corresponding to variations in the composition or the structure of their glycanic moiety. We have previously studied the different forms of alpha-L-fucosidase in human serum, kidney and urine. Some modifications of the glycanic fraction of glycoproteins have been described in various forms of tumoral cells; therefore, we have attempted to verify if the alpha-L-fucosidase of blood cells might be a useful marker in the diagnosis of leukemias, using the enzymic pattern obtained by chromatographic or electrofocusing methods. Detergent extracts from normal lymphocytes, submitted to ion-exchange chromatography as well as to chromatofocusing, revealed the presence of two forms of alpha-L-fucosidase, A and B, with respective pIs of 5.7 and 6.2. After treatment by neuraminidase, these two forms remain distinct, showing that the degrees of sialylation is not the only difference. Moreover, after desialylation, the two forms have not the same affinity for concanavalin A, an argument for the heterogeneity of the glycanic structures. The determination of the total activity, and of enzymic patterns of alpha-L-fucosidase from leukemic cells led to the observation of three types of modifications, in comparison with normal lymphocytes: quantitative variations in the total activity; variations in the proportions of the two forms; variations due to the modification of pIs. We have studied the lymphocytes from four patients with a hairy-cell leukemia (HCL), four patients with chronic lymphoid leukemia (CLL) and the MO cell-line, proceeding from a HCL. In all cases, the total fucosidase activity is strongly decreased in comparison with normal lymphocytes activity. The chromatofocusing pattern for CLL cells reveals the presence of the A and B forms, without modification of their eluting pH. A characteristic pattern is obtained with hairy cells, presenting only the B form, eluted in more acidic conditions. The normal lymphocytes in peripheral blood are for 80 per cent of the T phenotype, and the CLL lymphocytes exhibit the phenotypic markers B, as well as the hairy cells, but the MO cell-line acquires in culture the T markers. As these last cells express both the A and B forms of enzyme, the absence of the A form of alpha-L-fucosidase seems to be a marker of the HCL.(ABSTRACT TRUNCATED AT 400 WORDS)