scholarly journals Evidence for a free N-acetylneuraminic acid-hydroxylating enzyme in pig mandibular gland soluble fraction

1995 ◽  
Vol 305 (2) ◽  
pp. 459-464 ◽  
Author(s):  
C J Mukuria ◽  
W D Mwangi ◽  
A Noguchi ◽  
G P Waiyaki ◽  
T Asano ◽  
...  
Keyword(s):  
Molecular Oxygen ◽  
Soluble Fraction ◽  
Mandibular Gland ◽  
Neuraminic Acid ◽  
Time Dependent ◽  
Monovalent Cations ◽  
Acetylneuraminic Acid ◽  
Bivalent Cations ◽  
Unknown Component ◽  
Salt Fractionation

The activity of a free N-acetylneuraminic acid (Neu5Ac)-hydroxylating enzyme which converted Neu5Ac into N-glycolyl-neuraminic acid (Neu5Gc) was demonstrated in the soluble fraction of pig mandibular gland. The hydroxylation was possible only with NADPH as the electron donor. The apparent Km was 4.5 mM Neu5Ac. At 0.5 mM monovalent cations had no effect on the hydroxylation of Neu5Ac whereas bivalent cations gave varied inhibition capacities ranging from 14 to 75%. EDTA gave a time-dependent enhancement of activity. It was concluded that the enzyme does not require an exogenously added inorganic cofactor. Results from salt fractionation of the soluble fraction and the use of inhibitors such as mercurials suggested that the hydroxylation of Neu5Ac to Neu5Gc may involve other, as yet unknown, component(s) and the possibility of electrons donated by NADPH being transferred to activated molecular oxygen (second substrate). We propose to name this enzyme N-acetyl-neuraminic acid hydroxylase.

Regulation of HSP25 expression and phosphorylation in functionally overloaded rat plantaris and soleus muscles

2006 ◽  
Vol 100 (2) ◽  
pp. 451-456 ◽  
Author(s):  
Kimberly A. Huey
Keyword(s):  
Heat Shock ◽  
Muscle Hypertrophy ◽  
Soluble Fraction ◽  
Insoluble Fraction ◽  
Cytoskeletal Proteins ◽  
Time Dependent ◽  
Time Points ◽  
Hindlimb Muscle ◽  
Muscle Loading ◽  
Muscle Remodeling

Functional overload (FO) is a powerful inducer of muscle hypertrophy and both oxidative and mechanical stress in muscle fibers. Heat shock protein 25 (HSP25) may protect against both of these stressors, and its expression can be regulated by changes in muscle loading and activation. The primary purpose of the present study was to test the hypothesis that chronic FO increases HSP25 expression and phosphorylation (pHSP25) in hypertrophying rat hindlimb muscle. HSP25 and pHSP25 levels were quantified in soluble and insoluble fractions of the soleus and plantaris to determine whether 3 or 7 days of FO increase translocation of HSP25 and/or pHSP25 to the insoluble fraction. p38 protein and phosphorylation (p-p38) was measured to determine its association with changes in pHSP25. HSP25 mRNA showed time-dependent increases in both the soleus and plantaris with FO. Three or seven days of FO increased HSP25 and pHSP25 in the soluble fraction in both muscles, with a greater response in the plantaris. In the insoluble fraction, HSP25 was increased after 3 or 7 days in both muscles, whereas pHSP25 was only increased in the 7-day plantaris. p38 and p-p38 increased in the plantaris at both time points. In the soleus, p-p38 only increased after 7 days. These results show that FO is associated with changes in HSP25 expression and phosphorylation and suggest its role in the remodeling that occurs during muscle hypertrophy. Increases in HSP25 in the insoluble fraction suggest that it may help to stabilize actin and/or other cytoskeletal proteins during the stress of muscle remodeling.

scholarly journals Kinetic studies on the acid hydrolysis of the methyl ketoside of unsubstituted and O-acetylated N-acetylneuraminic acid

1973 ◽  
Vol 133 (4) ◽  
pp. 623-628 ◽  
Author(s):  
A. Neuberger ◽  
Wendy A. Ratcliffe
Keyword(s):  
Sialic Acid ◽  
Acid Hydrolysis ◽  
Model Compound ◽  
Kinetic Studies ◽  
Order Rate Constant ◽  
Neuraminic Acid ◽  
Acetylneuraminic Acid ◽  
Rate Of Hydrolysis ◽  
Ph Range ◽  
Hydrolysis Of

The hydrolysis of the model compound 2-O-methyl-4,7,8,9-tetra-O-acetyl-N-acetyl-α-d-neuraminic acid and neuraminidase (Vibrio cholerae) closely resembled that of the O-acetylated sialic acid residues of rabbit Tamm–Horsfall glycoprotein. This confirmed that O-acetylation was responsible for the unusually slow rate of acid hydrolysis of O-acetylated sialic acid residues observed in rabbit Tamm–Horsfall glycoprotein and their resistance to hydrolysis by neuraminidase. The first-order rate constant of hydrolysis of 2-methyl-N-acetyl-α-d-neuraminic acid by 0.05m-H2SO4 was 56-fold greater than that of 2-O-methyl-4,7,8,9-tetra-O-acetyl-N-acetyl -α-d-neuraminic acid. Kinetic studies have shown that in the pH range 1.00–3.30, the observed rate of hydrolysis of 2-methyl-N-acetyl-α-d-neuraminic acid can be attributed to acid-catalysed hydrolysis of the negatively charged CO2− form of the methyl ketoside.

A synthesis of N-acetylneuraminic acid and [6-2H]-N-acetyl-neuraminic acid from N-acetyl-d-glucosamine

1987 ◽  
Vol 164 ◽  
pp. 415-432 ◽  
Author(s):  
Radomir Julina ◽  
Ingrid Müller ◽  
Andrea Vasella ◽  
René Wyler
Keyword(s):  
Neuraminic Acid ◽  
Acetylneuraminic Acid

scholarly journals Facile Anomer-oriented Syntheses of 4-Methylumbelliferyl Sialic Acid Glycosides

2021 ◽  
Author(s):  
Abdullah Hassan ◽  
Stefan Oscarson
Keyword(s):  
Catalytic Activity ◽  
Sialic Acid ◽  
Substrate Specificity ◽  
Enzymatic Activity ◽  
Addition Reaction ◽  
Neuraminic Acid ◽  
Acetylneuraminic Acid ◽  
Diastereoselective Addition ◽  
High Yields ◽  
Stereoselective Syntheses

<p>As part of a program to find new sialidases and determine their enzymatic specificity and catalytic activity, a library of 4-methylumbelliferyl sialic acid glycosides derivatised at the C-5 position were prepared from <i>N</i>-acetylneuraminic acid. Both α- and β-4-methylumbelliferyl sialic acid glycosides were prepared in high yields and excellent stereoselectivity. Alpha anomers were accessed via reagent control by utilising additive CH<sub>3</sub>CN and TBAI, whereas the beta anomers were synthesised through a diastereoselective addition reaction of iodine and the aglycone to the corresponding glycal followed by reduction of the resulting 3-iodo compounds. Both anomer-oriented synthetic pathways allow for gram-scale stereoselective syntheses of the desired C-5 modified neuraminic acid derivatives for use as tools to quantify the enzymatic activity and substrate specificity of known<b> </b>sialidases, and potential detection and investigation of<b> </b>novel sialidases.</p>

Aerobic photolysis of methylcobalamin: structural and electronic properties of the Cbl–O–O–CH3 intermediate

2020 ◽  
Vol 49 (13) ◽  
pp. 4114-4124 ◽  
Author(s):  
Arghya Pratim Ghosh ◽  
Piotr Lodowski ◽  
Aida Bazarganpour ◽  
Marzena Leks ◽  
Pawel M. Kozlowski
Keyword(s):  
Density Functional Theory ◽  
Electronic Properties ◽  
Molecular Oxygen ◽  
Density Functional ◽  
Time Dependent ◽  
Functional Theory ◽  
Td Dft ◽  
Structural And Electronic Properties

Photolysis of methylcobalamin (MeCbl) in the presence of molecular oxygen (O2) has been investigated using density functional theory (DFT) and time-dependent DFT (TD-DFT).

Time-dependent quantum mechanical study of photodissociation of molecular oxygen in the Schumann–Runge continuum

2000 ◽  
Vol 112 (3) ◽  
pp. 1255-1259 ◽  
Author(s):  
N. Balakrishnan ◽  
M. J. Jamieson ◽  
A. Dalgarno ◽  
Y. Li ◽  
R. J. Buenker
Keyword(s):  
Molecular Oxygen ◽  
Time Dependent ◽  
Quantum Mechanical ◽  
Mechanical Study ◽  
Quantum Mechanical Study

scholarly journals Synthesis of 4-O-Alkylated N-Acetylneuraminic Acid Derivatives

2020 ◽  
Author(s):  
Emil Johansson ◽  
Rémi Caraballo ◽  
Mikael Elofsson
Keyword(s):  
Drug Discovery ◽  
Mammalian Cells ◽  
Natural Compounds ◽  
Neuraminic Acid ◽  
Synthetic Analogs ◽  
Acetylneuraminic Acid ◽  
Health And Disease ◽  
Alkylation Reactions

<p><i>N</i>-acetyl neuraminic acid<i> </i>(Neu5Ac) is a densely functionalized nine-carbon monosaccharide. It ubiquitously decorates the surface of mammalian cells were it is found in terminal positions of glycolipids and glycoproteins. This important saccharide and natural analogs play important roles in a number of processes in health and disease. Despite this few Neu5Ac based therapeutics have been developed. To further study and understand the chemistry and biology of Neu5Ac efficient protocols for synthesis of the parent natural compounds as well as synthetic analogs are required. In the manuscript, we report investigation of alkylation reactions to produce selectively modified Neu5Ac with focus on position 4. The study provides insights in the reaction and we establish robust protocols that allow selective modification of Neu5Ac for use as tool compounds and starting points for drug discovery.</p>

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