To date, rational redesign of glycosidase active-site clefts has been mainly limited to the removal of essential functionalities rather than their introduction. The glycoside hydrolase family 26 endo-beta-1,4-mannanase from the soil bacterium Cellulomonas fimi depolymerizes various abundant plant mannans. On the basis of differences in the structures and hydrolytic action patterns of this wild-type (but recombinantly expressed) enzyme and a homologous mannanase from Cellvibrio japonicus, two nonconserved amino acid residues at two distal glycone-binding subsites of the C. fimi enzyme were substituted, Ala323Arg at subsite -2 and Phe325Ala at subsite -3, to achieve inverted mannosyl affinities in the respective subsites, mimicking the Ce. japonicus enzyme that has an Arg providing mannosyl interactions at subsite -2. The X-ray crystal structure of the C. fimi doubly substituted mannanase was determined to 2.35 A resolution and shows that the introduced Arg323 is in a position suitable for hydrogen bonding to mannosyl at subsite -2. We report steady-state enzyme kinetics and hydrolysis-product analyses using anion-exchange chromatography and a novel rapid mass spectrometric profiling method of (18)O-labeled products obtained using H(2)(18)O as a solvent. The results obtained with oligosaccharide substrates show that although the catalytic efficiency (k(cat)/K(m)) is wild-type-like for the engineered enzyme, it has an altered hydrolytic action pattern that stems from promotion of substrate binding at subsite -2 (due to the introduced Arg323) and demotion of it at subsite -3 (to which removal of Phe325 contributed). However, k(cat)/K(m) decreased approximately 1 order of magnitude with polymeric substrates, possibly caused by spatial repositioning of the substrate at subsite -3 and beyond for the engineered enzyme.
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Head Neck
December 2024
Head and Neck Unit, The Royal Marsden Hospital, London, UK.
Background: To investigate the management of recurrent head and neck squamous cell carcinoma (rHNSCC) and describe survival outcomes.
Methods: Post hoc subgroup analysis of a retrospective national observational cohort was conducted. All patients with rHNSCC who received a definitive treatment decision between September 1, 2021 and November 30, 2021 were included.
Int J Biol Macromol
December 2024
College of Food Science and Engineering, Ocean University of China, 1299 Sansha Road, Qingdao 266404, China.
Carrageenans have attracted increasing research interests in recent decades for their various physicochemical and physiological properties. Random endo-acting carrageenases are promising tools for tailoring the molecular weight of carrageenan and preparing a series of carrageenan oligosaccharides. Although the processive ι-carrageenases in the GH82 family have been widely investigated, the random ι-carrageenase has not been reported.
View Article and Find Full Text PDFCancer
December 2024
Division of Public Health, Department of Family & Preventive Medicine, University of Utah School of Medicine, and Huntsman Cancer Institute, Salt Lake City, Utah, USA.
Introduction: The relations between coffee and tea consumption and head and neck cancer (HNC) incidence are unclear. With increasing global HNC burden, this study aims to examine the association between coffee, tea, and HNC.
Methods: A pooled analysis of 9548 HNC cases and 15,783 controls from 14 individual-level case-control studies was conducted from the International Head and Neck Cancer Epidemiology consortium.
J Craniomaxillofac Surg
December 2024
Department of Otolaryngology - Head and Neck Surgery, Giuseppe Fornaroli Hospital, ASST Ovest Milanese, Magenta, Milano, Italy; Doctoral Degree in Translational Research in Public Health and High Prevalence Diseases, UIB. Universitat de les Illes Balears, Palma de Mallorca, Spain.
Introduction: A growing amount of evidence points at lymph node yield (LNY) and lymph node ratio (LNR) as useful indicators in the prognostic evaluation of patients affected by head and neck squamous cell carcinoma (HNSCC) who require neck dissection. The aim of this study was to assess the importance of LNY and LNR in the prognostic evaluation of head and neck cancer patients.
Materials And Methods: Included studies were those examining LNY and/or LNR in head and neck cancer patients.
Am J Otolaryngol
December 2024
Department of Otolaryngology-Head and Neck Surgery, Jacobs School of Medicine and Biomedical Sciences, State University of New York at Buffalo, Buffalo, NY 14209, USA. Electronic address:
Objective: Trampolines are popular among children, but trampoline injuries constitute a large number of emergency department visits. The purpose of this study was to determine how often neck injuries occur among children with trampoline-related injuries and to identify the mechanism of injury.
Methods: We analyzed the National Electronic Injury Surveillance System (NEISS) database to characterize patient demographics, injury types, injury subsite, and emergency department disposition status associated with trampoline related neck injuries between 2012 and 2021 in the United States.
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