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Endo-1,4-β-xylanases (EC 3.2.1.8) hydrolyze the 1,4-β-D-xylosidic linkages in xylans, the most abundant hemicellulose in plant cell walls. Xylanase enzymes have numerous industrial applications, including the manufacturing of animal feed, bread, juice and wine, pulp and paper, and biofuels. In this study, two glycosyl hydrolase family 10 members designated GtXyn10A and GtXyn10B and two glycosyl hydrolase family 11 members, OpXyn11A and CcXyn11C, were functionally expressed and subjected to biochemical characterization. The K(M), V(max), and k(cat) values of the four xylanases, determined using birchwood xylan, ranged from 0.27 to 1.1 mg/mL, 130 to 980 μmol/min/mg, and 109 to 344 s⁻¹, respectively, where OpXyn11A gave the highest and GtXyn10B the lowest values for all three parameters. Substrate specificity studies and analysis of the products released during the degradation of xylo-oligosaccharides and three types of xylan revealed significant differences in catalytic properties, particularly between OpXyn11A and the other xylanases and between the family 10 and the family 11 xylanases. Molecular modeling suggests that the unique substrate specificity of OpXyn11A can be attributed to the presence of a serine rather that an asparagine or aspartate residue at the +1 substrate binding site. Additionally, all four xylanases exhibited biochemical characteristics of interest for various commercial applications.

A field trial was conducted to assess the efficacy of a combined prostaglandin F(2)alpha analogue (cloprostenol) and dexamethasone treatment as an abortifacient in feedlot heifers. Heifers were grouped according to stage of gestation as follows: Group I, one to four months, n = 37: group II, four to six months, n = 40: group III, six to eight months, n = 40: group IV, one to eight months, n = 29. Heifers in groups I, II and III received a simultaneous intramuscular injection of 500 mug cloprostenol and 25 mg dexamethasone at the time of rectal palpation for pregnancy diagnosis. Heifers in group IV were subjected to rectal palpation for pregnancy diagnosis but received no treatments. Heifers were observed daily for two weeks for abortion and rectal palpations were done 50 days after treatment to determine reproductive status. HEIFERS ABORTING AFTER TREATMENT WERE AS FOLLOWS: Group I, 37/37; group II, 37/40, group III, 37/40; group IV, 0/29. In each of groups II and III there was one pregnancy and two cases of fetal mummification. The numbers of abortions in groups I, II and III were significantly different from that in group IV (P