Human fibroblast stromelysin catalytic domain: expression, purification, and characterization of a C-terminally truncated form.

Stromelysin-1 is a member of a tissue metalloproteinase family whose members are all capable of degrading extracellular matrix components. A truncated form of human fibroblast prostromelysin 1 lacking the C-terminal, hemopexin-like domain has been expressed in Escherichia coli and purified to homogeneity. Treatment of this short form of prostromelysin with (aminophenyl)mercuric acetate resulted in activation and loss of the propeptide in a manner identical with the wild-type, full-length protein. Kinetic comparisons using Nle11-substance P as a substrate showed that the wild-type stromelysin and the truncated form of the enzyme had similar kcat and Km values. Likewise, both enzymes displayed similar Ki values for a hydroxamate-containing peptide inhibitor. Taken together, these results indicate that the C-terminal portion of stromelysin is not required for proper folding of the catalytic domain, maintenance of the enzyme in a latent form, activation with an organomercurial, cleavage of a peptide substrate, or interaction with an inhibitor. Moreover, the active short form of stromelysin displayed a reduction in the C-terminal heterogeneity, a characteristic degradation of the full-length stromelysin, and thereby provides a more suitable protein for future structural studies.     

Eucalypt leaf decomposition in an intermittent stream in south-eastern Australia

Eucalypt leaf packs were placed at two sites in an intermittent stream during summer to examine the hypothesis that terrestrially-exposed leaf litter accumulates a richer microbial flora than submerged leaves — a phenomenon observed in Canadian temporary vernal pools. This did not occur; during the experiment, microbial biomass (as ATP) rose steadily on submerged leaves but remained low on terrestrially-exposed leaves. Densities of most functional feeding groups on the submerged leaves increased with time. Scrapers appeared to be more important than shredders in eucalypt leaf breakdown at both sites.     

Identification and Distribution of Phenylacetic Acid in the Brain of the Rat

Abstract: Phenylacetic acid, the major metabolite of phenylethylamine, has been identified and quantitated in rat brain regions by capillary column high-resolution gas chromatography mass spectrometry. Its distribution is heterogeneous and correlates with that of phenylethylamine. The values obtained were (ng/g ± SEM): whole brain, 31.2 ± 2.7; caudate nucleus, 64.6 ± 6.5; hypothalamus, 60.1 ± 7.4; cerebellum, 31.3 ± 2.9; brainstem, 33.1 ± 3.3, and the "rest," 27.6 ± 3.0.     

Sural nerve oxygen tension in diabetes.

Peripheral nerve oxygen tensions were assessed in vivo by using microelectrodes to measure endoneurial oxygen tension in exposed sural nerve. In 11 diabetic patients with chronic sensorimotor neuropathy the mean endoneurial oxygen tension was 39.7 (SD 10.2) mm Hg. In all but one patient compared with none of four non-neuropathic subjects the mean nerve oxygen tensions were below dorsal foot vein values. This unphysiological state may have a role in the aetiology of diabetic neuropathy.     

Properties of Pseudomonas AM1 primary-amine dehydrogenase immobilized on agarose.

1. The primary-amine dehydrogenase of Pseudomonas AM1 (primary amine:(acceptor) oxidoreductase (deaminating), EC 1.4.99.-) was purified by an improved method and covalently attached to cyanogen bromide-activated Sepharose 4B. The immobilized enzyme showed very little change in its sensitivity to heat and to inhibition by semicarbazide as compared with the soluble enzyme, but had enhanced stability at 0 degrees C. The pH optimum of the immobilized enzyme remained unchanged at pH 7.4. 2. A new type of spectrophotometric assay is described in which sedimentation of the immobilized enzyme in the cuvette is prevented by increasing the viscosity by the presence of 10% (w/w) polyethylene glycol (M1 20 000). Detailed kinetic analysis using this assay showed only insignificant differences in the Km values for n-butylamine and phenazine methosulphate between the soluble and Agarose-bound enzymes. The results are compared with those for other oxidoreductase enzymes immobilized on Sepharose.