title: Comparison of biosynthesis and subcellular distribution of lysozyme and lysosomal enzymes in U937 monocytes.
abstract: Using metabolic labelling and sucrose density fractionation we compared the synthesis of lysozyme and lysosomal enzymes in human monocytic U937 cells. In pulse-chase experiments in sucrose density gradients, the intracellular radioactively labelled lysozyme distributed similarly to cathepsin D and beta-hexosaminidase. With the aid of immunochemical detection in Western blots, the steady-state distribution of lysozyme was found to be slightly different from that of beta-hexosaminidase; relatively more lysozyme was present in fractions sedimenting between lysosomes and the Golgi apparatus. The observed distribution of the lysozyme antigen with a prominent peak in the lysosomal fraction was in striking contrast to the broad distribution of the lysozyme activity. The difference was explained by a bias in the determination of the activity of lysozyme by the 'lysoplate' diffusion assay.
authors.forename: D K
authors.initials: DK
authors.lastname: Gupta
authors.forename: N
authors.initials: N
authors.lastname: Theisen
authors.forename: K
authors.initials: K
authors.lastname: von Figura
authors.forename: A
authors.initials: A
authors.lastname: Hasilik
mesh_terms: D002402:Cathepsin D / Q000032:analysis; D002460:Cell Line; D006596:Hexosaminidases / Q000032:analysis; D006801:Humans; D008247:Lysosomes / Q000201:enzymology*; D009000:Monocytes / Q000201:enzymology*; D009113:Muramidase / Q000032:analysis / Q000096:biosynthesis*; D013347:Subcellular Fractions / Q000201:enzymology; D001619:beta-N-Acetylhexosaminidases
chemical_list: D006596:Hexosaminidases; D009113:Muramidase; D001619:beta-N-Acetylhexosaminidases; D002402:Cathepsin D