1. The N-acetyl-beta-glucosaminidase of human spleen has been separated by gel electrophoresis into two components, an acidic form A and a basic form B. 2. The two forms are readily separated on DEAE-cellulose and have been concentrated 50-fold and sevenfold respectively. 3. They show similar K(m) values towards 4-methylumbelliferyl N-acetyl-beta-d-glucosaminide, and have the same pH optima when compared in citrate, phosphate or acetate buffers. They are inhibited to a similar extent by acetate, heparin, N-acetylgalactosaminolactone, N-acetyl-beta-d-galactosamine and N-acetyl-beta-d-glucosamine. Specificity for C-4 orientation is not absolute and p-nitrophenyl beta-galactosaminide is also hydrolysed but at a rate only 11.6% of that for the corresponding glucosaminide. 4. N-Acetyl-beta-glucosaminidase B is stable over a wider pH range than is N-acetyl-beta-glucosaminidase A, and is less easily denatured by heat. 5. Tissue fractionation indicates that both the A and B forms are present in the lysosomal fraction, whereas the supernatant contains the A form only. 6. Evidence is presented to indicate that the A form contains a number of sialic acid residues.

Various phenoxazine, phenothiazine, phenazine, indophenol and bipyridilium derivatives were tested for their effectiveness as redox mediators in microbial fuel cells containing Alcaligenes eutrophus, Bacillus subtilis, Escherichia coli, or Proteus vulgaris as the active biological agent, and glucose or succinate as the oxidisable substrate. A ferricyanide-Pt cathode was used. The open-circuit cell e.m.f.'s increased in the order of increasing negative formal redox potentials at pH 7(Ez) of the redox compounds. Several of the redox agents worked well as mediators, maintaining steady currents over several hours, and thionine was found to be particularly effective in maintaining relatively high cell voltages when current was drawn from the cell. A number of the compounds tested did not function well, either because they were incompletely or slowly reduced by the microorganisms or because of their instability. P. vulgaris, with thionine as mediator and glucose as substrate, showed the best performance in a fuel cell. This system was examined in some detail under various conditions of external load to establish the effects of organism concentration, mediator concentration, and substrate addition. Coulombic outputs from these cells were calculated by integration of the current-time plots. Coulombic yields of 30-60% were obtained, on the basis of (theoretical) complete oxidation of added substrate to C02 and water.

Potentiometric and amperometric measurements were made with microbial fuel cells containing E. coli or yeast as the anodic reducing agent and glucose as the oxidizable substrate. The catalytic effects of thionine and resorufin on the anode reaction were investigated. Results on the potentiometry, polarization, and coulombic output of the cells support a mediator-coupled mechanism for the transfer of electrons from the organism to the electrode in preference to a mechanism of "direct" electrochemical oxidation of glucose or its degradation products. Experiments with (14)C-labeled glucose show that when a microbial fuel cell produces a current under load, exogenous glucose is metabolized to produce (14)CO(2). The Coulombic yields of the cells indicate a high degree of energy conversion in these systems.

Redox mediators promote electron transfer in microbial fuel cells. The reduction of a range of redox mediators by bacteria was studied in some detail in order to identify effective mediator—organism combinations. Rates of reduction of mediator dyes by bacteria were measured spectrophotometrically at 30°C under anaerobic conditions for standardised concentrations of organism, substrate and dye. The kinetics of dye reduction showed two general patterns: a simple, exponential curve or a complex curve with an initial linear rate followed by a faster exponential rate of reduction. Dye‐reduction rates were greater than rates of oxygen consumption (QO2) for several combinations of organism and redox dye. Thionine, brilliant cresyl blue, methylene blue and benzyl viologen were tested in combination with Alcaligenes eutrophus, Azotobacter chroococcum, Bacillus subtilis, Escherichia coli, Proteus vulgaris, Pseudomonas aeruginosa and Pseudomonas putida, using glucose and succinate as substrates. Rates of reduction of alizarin brilliant blue, 2,6‐dichlorophenolindophenol, gallocyanine, new methylene blue, N,N‐dimethyl‐disulphonated thionine, phenazine ethosulphate, resorufin, safranine‐O, phenothiazinone and toluidine blue‐O were also measured with Pr. vulgaris only. For E. coli, both QO2 and the rate of thionine reduction increased with increasing temperature in the range 25 to 37°C, but for Pr. vulgaris thionine reduction rates did not correlate with temperature in this way. Dye‐reduction rates and QO2 for Az. chroococcum were dependent on the components of the washing solution and/or the temperature at which cell suspensions were prepared. The results are discussed in relation to the use of these dyes as electron‐transfer mediators in microbial fuel cells.

Mutations in the PKD1 gene are responsible for 85% of cases of autosomal dominant polycystic kidney disease (ADPKD). This gene encodes a large membrane associated glycoprotein, polycystin-1, which is predicted to contain a number of extracellular protein motifs, including a C-type lectin domain between amino acids 403--532. We have cloned and expressed the PKD1 C-type lectin domain, and have demonstrated that it binds carbohydrate matrices in vitro, and that Ca(2+) is required for this interaction. This domain also binds to collagens type I, II and IV in vitro. This binding is greatly enhanced in the presence of Ca(2+) and can be inhibited by soluble carbohydrates such as 2-deoxyglucose and dextran. These results suggest that polycystin-1 may be involved in protein-carbohydrate interactions in vivo. The data presented indicate that there may a direct interaction between the PKD1 gene product and an ubiquitous extracellular matrix (ECM) protein.