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261.
Large aggregating and small leucine-rich proteoglycans are degraded by different pathways and at different rates in tendon. 总被引:2,自引:0,他引:2
Tom Samiric Mirna Z Ilic Christopher J Handley 《European journal of biochemistry》2004,271(17):3612-3620
This work investigated the kinetics of catabolism and the catabolic fate of the newly synthesized (35)S-labelled proteoglycans present in explant cultures of tendon. Tissue from the proximal region of bovine deep flexor tendon was incubated with [(35)S]sulfate for 6 h and then placed in explant cultures for periods of up to 15 days. The amount of radiolabel associated with proteoglycans and free [(35)S]sulfate lost to the medium and retained in the matrix was determined for each day in culture. It was shown that the rate of catabolism of radiolabelled small proteoglycans (decorin and biglycan) was significantly slower (T((1/2)) > 20 days) compared with the radiolabelled large proteoglycans (aggrecan and versican) that were rapidly lost from the tissue (T((1/2)) approximately 2 days). Both the small and large newly synthesized proteoglycans were lost from the matrix with either intact or proteolytically modified core proteins. When explant cultures of tendon were maintained either at 4 degrees C or in the presence of the lysosomotrophic agent ammonium chloride, inhibition of the cellular catabolic pathway for small proteoglycans was demonstrated indicating the involvement of cellular activity and lysosomes in the catabolism of small proteoglycans. It was estimated from these studies that approximately 60% of the radiolabelled small proteoglycans that were lost from the tissue were degraded by the intracellular pathway present in tendon cells. This work shows that the pathways of catabolism for large aggregating and small leucine-rich proteoglycans are different in tendon and this may reflect the roles that these two populations of proteoglycans play in the maintenance of the extracellular matrix of tendon. 相似文献
262.
Christopher J. Handley Meng Tuck Mok Mirna Z. Ilic Clair Adcocks David J. Buttle H. Clem Robinson 《Matrix biology》2001,20(8):531-553
Bovine aggrecan was digested with bovine cathepsin D at pH 5.2 under conditions of partial digestion and the resulting aggrecan core protein fragments were separated by electrophoresis on gradient polyacrylamide gels. The fragments were characterized by their reactivity to specific antibodies and by N-terminal amino acid sequencing. It was also demonstrated that cathepsin D cleaved bovine aggrecan at five sites within the core protein, between residues Phe(342)-Phe(343) in the interglobular domain, Leu(1462)-Val(1463) between the chondroitin sulfate attachment regions 1 and 2 and Leu(1654)-Val(1655), Phe(1754)-Val(1755) and Leu(1854)-Ile(1855) that are located within the chondroitin sulfate attachment region 2 of the core protein. The time course of digestion showed that there was a continued degradation of aggrecan and there was no preferential cleavage of the core protein at any one site. It was shown that cathepsin D digested aggrecan over the pH range 5.2-6.5 resulting in the same products. When bovine cartilage was maintained in explant culture at pH 5.2 there was a rapid loss of both radiolabeled and chemical pools of sulfated glycosaminoglycans into the culture medium and this loss was inhibited by the inclusion in the medium of the aspartic proteinase inhibitor, pepstatin A. The aggrecan core protein fragments appearing in the medium of cultures maintained at pH 5.2 were characterized and it was shown that the fragments had N-terminal sequences starting at Phe(343), Ile(1855), and Val(1755) or Val(1463). This work demonstrates that cathepsin D present within the extracellular matrix of articular cartilage has the potential to contribute to the proteolytic processing of the core protein of aggrecan in this tissue. 相似文献
263.
Mariana Provedel Martins Ana Maria Mouad Letícia Boschini Mirna Helena Regali Seleghim Lara Dur?es Sette André Luiz Meleiro Porto 《Marine biotechnology (New York, N.Y.)》2011,13(2):314-320
Whole cells of the marine fungi Aspergillus sydowii Gc12, Penicillium raistrickii Ce16, P. miczynskii Gc5, and Trichoderma sp. Gc1, isolated from marine sponges of the South Atlantic Ocean (Brazil), have been screened for the enzymatic resolution
of (±)-2-(benzyloxymethyl)oxirane (benzyl glycidyl ether; 1). Whole cells of A. sydowii Gc12 catalyzed the enzymatic hydrolysis of (R,S)-1 to yield (R)-1 with an enantiomeric excess (ee) of 24–46% and 3-(benzyloxy)propane-1,2-diol (2) with ee values <10%. In contrast, whole cells of Trichoderma sp. Gc1 afforded (S)-1 with ee values up to 60% and yields up to 39%, together with (R)-2 in 25% yield and an ee of 32%. This is the first published example of the hydrolysis of 1 by whole cells of marine fungi isolated from the South Atlantic Ocean. The hydrolases from the two studied fungi exhibited
complementary regioselectivity in opening the epoxide ring of racemic 1, with those of A. sydowii Gc12 showing an (S) preference and those of Trichoderma sp. Gc1 presenting an (R) preference for the substrate. 相似文献
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Nelma Regina Segnini Bossolan Mirna Januária Leal Godinho Antonia Garcia Torres Volpon 《World journal of microbiology & biotechnology》2005,21(8-9):1471-1475
Summary The changes that occur in cell size and shape during experimental starvation and resuscitation of bacteria may find practical
application in the biotechnological processes used in microbial enhanced oil-recovery (MEOR), in in situ bioremediation and in the creation of biobarriers. In the work described here, the aim was to observe certain aspects of
the response of a strain of Klebsiella pneumoniae, isolated from oil producer wells belonging to PETROBRAS (National Oil Company of Brazil), to starvation and growth under
various culture conditions. Cells of K. pneumoniae were taken from an exponentially-growing culture, washed and suspended in phosphate-buffered saline solution, without nutrients,
where they remained for 91 days. Aliquots were withdrawn periodically, to perform viable and total cell counts and measure
the optical density and cell dimensions. The starved cells were resuspended in sodium citrate medium, where they recuperated
and exhibited a typical growth curve. The results indicate that this strain is a viable option for future trials on the transport
and growth of microorganisms inside porous media, aimed at possible applications in MEOR. 相似文献