The xylanase activity of StCel5A might also explain why StCel5A also promotes Glc yields, because xylanases are known to enhance the accessibility of cellulose to cellulases. StCel5A also had better activity than TrCel5A against various b1,4-mannans, including two types of galactomannan and unsubstituted mannan. Because corn stover contains small amounts of galactose or Man compared to Glc and Xyl, it is unlikely that mannanase activity instead of xylanase activity accounts for the superiority of StCel5A, and, in fact, no release of Man from corn stover could be measured with StCel5A. Furthermore, we NVP-BEZ235 earlier showed in a 16-component optimization experiment that b-mannanase makes no contribution to Glc or Xyl release from pretreated corn stover. A structural understanding of the basis of substrate specificity in glycosyl hydrolases has been challenging. Chen et al. analyzed the basis of substrate discrimination between glucan and galactomannan across the entire GH5 family. They identified a motif of six amino acids that when mutated altered substrate specificity, using Cel5A from the bacterium Thermotaga maritima as the model.

TmCel5A is in subfamily 25 of GH5 and can hydrolyze both cellulose and galactomannan, like StCel5A. Four of the six critical amino acids identified by Chen et al. could be unambiguosly identified in StCel5A and TrCel5A despite low overall amino acid identity. Among these six critical amino acids, His95 was invariant in all three sequences, while the other residues varied but in a pattern that did not correlate with the known substrate specificity of the three enzymes. For example, in TmCel5A, TrCel5A, or StCel5A, respectively, amino acid 53 was Pro, Pro, or Asp; amino acid 96 was His, Asn, or Asn; and amino acid 287 was Asp, Ala, or Gly. Thus, substrate discrimination appears to follow different rules in subfamily 5 of GH5 than in subfamily 25. The superiority of StCel5A over TrCel5A might also be due to features of the two enzymes that are unrelated to substrate specificity. This is supported by the fact that two other members of GH5_5_2 are not active against xylan, unlike StCel5A. The homing and early transdifferentiation of the transplanted BMMSCs in the injured gut appear to play a LDN-193189 beneficial role in mucosal regeneration. Compared to untreated animals, BMMSCs transplantation leads to increases in the overall thickness of the mucosa as well as the relative areas of the crypts in the intestine.

Therefore, our findings support the notion that bone marrow stem cell therapy may be useful in the treatment of inflammatory bowl diseases. Certain soluble growth factors may play a critical role for mobilization, survival and successful integration of circulating multipotent stem cells in the target organs/tissue, which may be also of value in stem cell therapy for degenerative diseases. Adjunctive use of stem cell trophic factors has been shown to improve the outcome of BMMSCs therapy in a number of disease conditions, therefore are recommended in clinical trials of stem cell therapy. In the present study we demonstrate that the stem cell factor alone can improve the intestinal mucosal regeneration following indomethacin-induced injury for a certain degree. Coadministration of this factor appears to exhibit a synergistic beneficial effect on BMMSCs transplant to intestinal recovery.