Possibility of inborn defect in isovalericacidaemia involving altered enzyme specificity rather than total inactivity

Nature ◽  
1974 ◽  
Vol 248 (5444) ◽  
pp. 140-142 ◽  
Author(s):  
P. C. ENGEL
Keyword(s):  
Enzyme Specificity ◽  
Inborn Defect

Human Neuraminidases Have Reduced Activity Towards Modified Sialic Acids on Glycoproteins

2020 ◽  
Author(s):  
Carmanah D. Hunter ◽  
Elizabeth Porter ◽  
Christopher Cairo
Keyword(s):  
Substrate Specificity ◽  
General Trend ◽  
Sialic Acids ◽  
Enzyme Specificity ◽  
Naturally Occurring ◽  
Bovine Submaxillary Mucin ◽  
Reduced Activity

This work investigated the substrate specificity of hNEU enzymes for a glycoprotein substrate (bovine submaxillary mucin) containing 9-<i>O</i>-acetylated and Neu5Gc residues. Using this model substrate, we observe a general trend for hNEU tolerance of Neu5Ac>Neu5Gc>>>Neu5,9Ac<sub>2</sub>, consistent with our previous results with glycolipid substrates. These results expand our understanding of hNEU enzyme specificity and suggest that naturally occurring modifications of sialic acids can play a role in regulating hNEU activity.

Reversing enzyme specificity

Nature ◽  
1989 ◽  
Vol 339 (6226) ◽  
pp. 580-581 ◽  
Author(s):  
Thomas L. Poulos
Keyword(s):  
Enzyme Specificity

Lid domain plasticity and lipid flexibility modulate enzyme specificity in human monoacylglycerol lipase

2017 ◽  
Vol 1862 (5) ◽  
pp. 441-451 ◽  
Author(s):  
Laura Riccardi ◽  
Jose M. Arencibia ◽  
Luca Bono ◽  
Andrea Armirotti ◽  
Stefania Girotto ◽  
...  
Keyword(s):  
Enzyme Specificity ◽  
Monoacylglycerol Lipase ◽  
Lid Domain

scholarly journals Mi2β Shows Chromatin Enzyme Specificity by Erasing a DNase I-hypersensitive Site Established by ACF

2009 ◽  
Vol 284 (12) ◽  
pp. 7533-7541 ◽  
Author(s):  
Haruhiko Ishii ◽  
Hansen Du ◽  
Zhaoqing Zhang ◽  
Angus Henderson ◽  
Ranjan Sen ◽  
...  
Keyword(s):  
Dnase I ◽  
Enzyme Specificity ◽  
Hypersensitive Site ◽  
Dnase I Hypersensitive Site

scholarly journals The Methionine 549 and Leucine 552 Residues of Friedelin Synthase from Maytenus ilicifolia Are Important for Substrate Binding Specificity

Molecules ◽  
2021 ◽  
Vol 26 (22) ◽  
pp. 6806
Author(s):  
Bruna F. Mazzeu ◽  
Tatiana M. Souza-Moreira ◽  
Andrew A. Oliveira ◽  
Melissa Remlinger ◽  
Lidiane G. Felippe ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Biological Activities ◽  
Site Directed Mutagenesis ◽  
Directed Mutagenesis ◽  
Enzyme Specificity ◽  
Amino Acid Residues ◽  
Loss Of Function ◽  
Pentacyclic Triterpene ◽  
Oxidosqualene Cyclases ◽  
Maytenus Ilicifolia

Friedelin, a pentacyclic triterpene found in the leaves of the Celastraceae species, demonstrates numerous biological activities and is a precursor of quinonemethide triterpenes, which are promising antitumoral agents. Friedelin is biosynthesized from the cyclization of 2,3-oxidosqualene, involving a series of rearrangements to form a ketone by deprotonation of the hydroxylated intermediate, without the aid of an oxidoreductase enzyme. Mutagenesis studies among oxidosqualene cyclases (OSCs) have demonstrated the influence of amino acid residues on rearrangements during substrate cyclization: loss of catalytic activity, stabilization, rearrangement control or specificity changing. In the present study, friedelin synthase from Maytenus ilicifolia (Celastraceae) was expressed heterologously in Saccharomyces cerevisiae. Site-directed mutagenesis studies were performed by replacing phenylalanine with tryptophan at position 473 (Phe473Trp), methionine with serine at position 549 (Met549Ser) and leucine with phenylalanine at position 552 (Leu552Phe). Mutation Phe473Trp led to a total loss of function; mutants Met549Ser and Leu552Phe interfered with the enzyme specificity leading to enhanced friedelin production, in addition to α-amyrin and β-amyrin. Hence, these data showed that methionine 549 and leucine 552 are important residues for the function of this synthase.

scholarly journals Increased activity of a specific sialyltransferase in chronic myelogenous leukemia

Blood ◽  
1985 ◽  
Vol 66 (5) ◽  
pp. 1068-1071 ◽  
Author(s):  
MA Baker ◽  
RN Taub ◽  
A Kanani ◽  
I Brockhausen ◽  
A Hindenburg
Keyword(s):  
Enzyme Activity ◽  
Sialic Acid ◽  
Chronic Myelogenous Leukemia ◽  
Lectin Binding ◽  
Myelogenous Leukemia ◽  
Membrane Properties ◽  
Enzyme Specificity ◽  
Membrane Glycoproteins ◽  
Sialyltransferase Activity ◽  
Acceptor Group

Granulocytes from patients with chronic myelogenous leukemia (CML) are morphologically identical to their normal counterparts but show marked differences in circulation patterns and in some membrane properties. We have previously shown that there is abnormal lectin binding to CML granulocytes, and aberrant sialylation of membrane glycoproteins. To examine the changes in sialylation of CML granulocytes further, we have studied membrane preparations from CML and normal granulocytes for specific sialyltransferase activity. Because sialyltransferase enzymes are specific for the configuration of the acceptor group, enzyme activity was assayed by measuring transfer of sialic acid from CMP-14C- sialic acid to substrates of defined structure. As compared with those of normal counterparts, CML extracts catalyzed a 50% higher overall rate of sialylation of asialofetuin, a substrate possessing both N- and O-linked acceptors. Studies of enzyme specificity utilizing porcine and ovine submaxillary mucins, antifreeze glycoprotein and alpha-1 acid glycoprotein as acceptors showed that the increased sialylation by CML extracts was due primarily to substrates with the O-linked Gal beta 1--- -3GaINAc acceptor group. These data suggest that sialyltransferase activity is increased in CML granulocytes compared to normal granulocytes and that the increased enzyme activity is specific for O- linked Gal beta 1----3GaINAc. This enzyme activity may be directly responsible for the abnormal membrane sialylation and pathophysiological behavior of these cells.

scholarly journals Biochemical characterization of a glycoside hydrolase family 43 β-D-galactofuranosidase from the fungus Aspergillus niger

2021 ◽  
Author(s):  
Gregory S Bulmer ◽  
Fang Wei Yuen ◽  
Naimah Begum ◽  
Bethan S Jones ◽  
Sabine S Flitsch ◽  
...  
Keyword(s):  
Aspergillus Niger ◽  
Glycoside Hydrolase ◽  
Biochemical Characterization ◽  
Maximum Activity ◽  
Glycoside Hydrolase Family ◽  
Enzyme Specificity ◽  
Fungal Enzymes ◽  
Glycoside Hydrolase Family 43 ◽  
Hydrolase Family

β-D-Galactofuranose (Galf) and its polysaccharides are found in bacteria, fungi and protozoa but do not occur in mammalian tissues, and thus represent a specific target for anti-pathogenic drugs. Understanding the enzymatic degradation of these polysaccharides is therefore of great interest, but the identity of fungal enzymes with exclusively galactofuranosidase activity has so far remained elusive. Here we describe the identification and characterization of a galactofuranosidase from the industrially important fungus Aspergillus niger. Phylogenetic analysis of glycoside hydrolase family 43 subfamily 34 (GH43_34) members revealed the occurrence of three distinct clusters and, by comparison with specificities of characterized bacterial members, suggested a basis for prediction of enzyme specificity. Using this rationale, in tandem with molecular docking, we identified a putative β-D-galactofuranosidase from A. niger which was recombinantly expressed in Escherichia coli. The Galf-specific hydrolase, encoded by xynD demonstrates maximum activity at pH 5, 25 °C towards 4-Nitrophenyl-β-galactofuranoside (pNP-βGalf), with a Km of 17.9 ± 1.9 mM and Vmax of 70.6 ± 5.3 μmol min-1. The characterization of this first fungal GH43 galactofuranosidase offers further molecular insight into the degradation of Galf-containing structures and may inform clinical treatments against fungal pathogens.

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