Human chorionic β‐mannosidase: Comparison with β‐mannosidase from human cultured fibroblasts

Abstract The conditions for assay of β‐mannosidase activity in human chorionic villi (CV) were studied using the fluorogenic substrate 4‐methylumbelliferyl‐β‐D‐mannopyranoside. A comparison of the biochemical properties of the CV β‐mannosidase with those of the enzyme from human cultured fibroblasts showed their similarity. Like the enzyme from skin fibroblasts, the CV β‐mannosidase had rather high activity. Both enzymes had virtually the same pH optimum (4.2‐4.7) and K m value. The data presented suggest that chorion biopsy specimens can be used for prenatal determination of β‐mannosidase activity at an early stage of development.