scholarly journals Pyridine Nucleosidase in Bull Semen ll. Biochemical Properties

1975 ◽  
Vol 28 (3) ◽  
pp. 273 ◽  
Author(s):  
KH Giles ◽  
KL Macmillan
Keyword(s):  
Enzyme Activity ◽  
Biochemical Properties ◽  
Time Intervals ◽  
Preliminary Heating ◽  
Bull Semen ◽  
Enzyme Denaturation ◽  
Inhibited Enzyme ◽  
Single Enzyme

It is most likely a single enzyme (NAD+ nucleosidase) present in semen from most bulls which hydrolyses the ribosyl pyridinium bond in both NAD and NADP. This conclusion is based on the following results: (i) each of 12 semen samples containing nucleosidase activity hydrolysed NAD at the same rate as NADP (r = 0�99); (ii) other untreated semen samples from different bulls which did not hydrolyse NAD were also inactive against NADP; (iii) enzyme denaturation produced by preliminary heating of semen filtrates for 15 min at varied temperatures or by heating at 55�C for varied time intervals caused similar reductions in the rates of NAD and NADP hydrolysis; and (iv) nicotinamide inhibited enzyme activity to the same degree using either NAD or NADP as the substrate.

Phosphatase systems in Fasciolopsis buski Lankester, 1857 and Gastrodiscus aegyptiacus Cobbold, 1876

Parasitology ◽  
1973 ◽  
Vol 67 (2) ◽  
pp. 197-204 ◽  
Author(s):  
Madan M. Goil
Keyword(s):  
Enzyme Activity ◽  
Tartaric Acid ◽  
Maximum Activity ◽  
Nitrophenyl Phosphate ◽  
Biochemical Studies ◽  
Phosphate Hydrolysis ◽  
Fasciolopsis Buski ◽  
Enzyme I ◽  
Inhibited Enzyme ◽  
Acid Phosphomonoesterase

Biochemical studies on the non-specific phosphomonoesterases have demonstrated the presence of acid phosphomonoesterase with maximum activity at pH 4·0 in Gastrodiscus aegyptiacus (enzyme I) and at pH 4·5 in the case of Fasdolopsis buski (enzyme II). The Km for ρ-nitrophenyl phosphate hydrolysis was 0·66 mM for enzyme I and 1·1 mM for enzyme II. Different concentrations of fluoride, arsenate, tartrate, tartaric acid, cysteine and copper brought about inhibition of both enzymes and magnesium, iodoaeetate, iodoacetamide and EDTA had no influence on either enzyme activity. Cobalt activated both enzymes while zinc inhibited enzyme I and strongly stimulated enzyme II.

scholarly journals Can Nanoimpacts Detect Single-Enzyme Activity? Theoretical Considerations and an Experimental Study of Catalase Impacts

ACS Catalysis ◽  
2016 ◽  
Vol 6 (12) ◽  
pp. 8313-8320 ◽  
Author(s):  
Enno Kätelhön ◽  
Lior Sepunaru ◽  
Arkady A. Karyakin ◽  
Richard G. Compton
Keyword(s):  
Experimental Study ◽  
Enzyme Activity ◽  
Theoretical Considerations ◽  
Single Enzyme

Coenzyme A metabolism

1985 ◽  
Vol 248 (1) ◽  
pp. E1-E9 ◽  
Author(s):  
J. D. Robishaw ◽  
J. R. Neely
Keyword(s):  
Enzyme Activity ◽  
Cardiac Muscle ◽  
Heart Muscle ◽  
Coenzyme A ◽  
Free Carnitine ◽  
Pantothenate Kinase ◽  
Acetyl Coenzyme A ◽  
Synthetic Pathway ◽  
And Control ◽  
Inhibited Enzyme

The metabolism of coenzyme A and control of its synthesis are reviewed. Pantothenate kinase is an important rate-controlling enzyme in the synthetic pathway of all tissues studied and appears to catalyze the flux-generating reaction of the pathway in cardiac muscle. This enzyme is strongly inhibited by coenzyme A and all of its acyl esters. The cytosolic concentrations of coenzyme A and acetyl coenzyme A in both liver and heart are high enough to totally inhibit pantothenate kinase under all conditions. Free carnitine, but not acetyl carnitine, deinhibits the coenzyme A-inhibited enzyme. Carnitine alone does not increase enzyme activity. Thus changes in the acetyl carnitine-to-carnitine ratio that occur with nutritional states provides a mechanism for regulation of coenzyme A synthetic rates. Changes in the rate of coenzyme A synthesis in liver and heart occurs with fasting, refeeding, and diabetes and in heart muscle with hypertrophy. The pathway and regulation of coenzyme A degradation are not understood.

scholarly journals Biological and biochemical properties in evaluation of forest soil quality

2014 ◽  
Vol 56 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Ewa Błońska ◽  
Jarosław Lasota
Keyword(s):  
Enzyme Activity ◽  
Forest Soil ◽  
Soil Quality ◽  
Soil Ph ◽  
Chemical Properties ◽  
Biochemical Properties ◽  
Essential Elements ◽  
Forest Site ◽  
Physico Chemical ◽  
Density And Biomass

Abstract The aim of this study was to assess the possibility of using biological and biochemical parameters in the evaluation of forest soil quality and changes caused by land use. The study attempted to determine a relationship between the enzymatic activity of soil, the number of earthworms and soil physico-chemical properties. The study was carried out in central Poland in adjoining Forest Districts (Przedbórz and Smardzewice). In soil samples taken from 12 research plots, basic physico-chemical properties, enzyme activity (dehydrogenase, urease) and density and biomass of earthworms were examined. Enzyme activity showed a large diversity within the forest site types studied. The correlations between the activity of the enzymes studied and C/N ratio indicated considerable importance of these enzymes in metabolism of essential elements of organic matter of forest soils. Urease and dehydrogenase activity and earthworm number showed susceptibility to soil pH, which confirmed relationships between enzyme activity and abundance of earthworms and soil pH in H2O and KCl.

scholarly journals Effects of Substrate-Binding Site Residues on the Biochemical Properties of a Tau Class Glutathione S-Transferase from Oryza sativa

Genes ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 25 ◽  
Author(s):  
Xue Yang ◽  
Jinchi Wei ◽  
Zhihai Wu ◽  
Jie Gao
Keyword(s):  
Amino Acids ◽  
Enzyme Activity ◽  
Abiotic Stress ◽  
Binding Site ◽  
Stress Responses ◽  
Stress Resistance ◽  
Substrate Binding ◽  
Biochemical Properties ◽  
Biotic And Abiotic Stress ◽  
Substrate Binding Site

Glutathione S-transferases (GSTs)—an especially plant-specific tau class of GSTs—are key enzymes involved in biotic and abiotic stress responses. To improve the stress resistance of crops via the genetic modification of GSTs, we predicted the amino acids present in the GSH binding site (G-site) and hydrophobic substrate-binding site (H-site) of OsGSTU17, a tau class GST in rice. We then examined the enzyme activity, substrate specificity, enzyme kinetics and thermodynamic stability of the mutant enzymes. Our results showed that the hydrogen bonds between Lys42, Val56, Glu68, and Ser69 of the G-site and glutathione were essential for enzyme activity and thermal stability. The hydrophobic side chains of amino acids of the H-site contributed to enzyme activity toward 4-nitrobenzyl chloride but had an inhibitory effect on enzyme activity toward 1-chloro-2,4-dinitrobenzene and cumene hydroperoxide. Different amino acids of the H-site had different effects on enzyme activity toward a different substrate, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole. Moreover, Leu112 and Phe162 were found to inhibit the catalytic efficiency of OsGSTU17 to 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole, while Pro16, Leu112, and Trp165 contributed to structural stability. The results of this research enhance the understanding of the relationship between the structure and function of tau class GSTs to improve the abiotic stress resistance of crops.

Regulation of Chloramphenicol Synthesis in Streptomyces sp. 3022a. 3-Deoxy-D-arabino-heptulosonate 7-Phosphate Synthetase

1971 ◽  
Vol 49 (4) ◽  
pp. 448-455 ◽  
Author(s):  
D. A. Lowe ◽  
D. W. S. Westlake
Keyword(s):  
Enzyme Activity ◽  
Shikimic Acid ◽  
Aromatic Amino Acids ◽  
Product Inhibition ◽  
Enzyme Synthesis ◽  
Synthetase Activity ◽  
Shikimic Acid Pathway ◽  
Sugar Phosphates ◽  
Acid Pathway ◽  
Single Enzyme

The repression and end-product inhibition of 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP) synthetase were studied in a chloramphenicol-producing Streptomycetes. Synthesis of DAHP synthetase was repressed by p-hydroxybenzoate, and enzyme activity was inhibited competitively by sugar phosphates, especially D-ribose 5-phosphate. The presence of chloramphenicol, aromatic amino acids, or shikimic acid pathway intermediates did not repress enzyme synthesis nor inhibit enzyme activity. Chloramphenicol production by growing cultures was not affected by the intermediates or end products of the shikimic acid pathway nor by the repression of DAHP synthetase. Purification of DAHP synthetase activity indicated the presence of a single enzyme protein with a molecular weight of 88 000.

scholarly journals Correspondence on “Can Nanoimpacts Detect Single-Enzyme Activity? Theoretical Considerations and an Experimental Study of Catalase Impacts”

ACS Catalysis ◽  
2017 ◽  
Vol 7 (5) ◽  
pp. 3591-3593 ◽  
Author(s):  
Alina N. Sekretaryova ◽  
Mikhail Yu. Vagin ◽  
Anthony P. F. Turner ◽  
Mats Eriksson
Keyword(s):  
Experimental Study ◽  
Enzyme Activity ◽  
Theoretical Considerations ◽  
Single Enzyme

scholarly journals Reply to Comment on “Can Nanoimpacts Detect Single-Enzyme Activity? Theoretical Considerations and an Experimental Study of Catalase Impacts”

ACS Catalysis ◽  
2017 ◽  
Vol 7 (5) ◽  
pp. 3594-3596 ◽  
Author(s):  
Enno Kätelhön ◽  
Lior Sepunaru ◽  
Arkady A. Karyakin ◽  
Richard G. Compton
Keyword(s):  
Experimental Study ◽  
Enzyme Activity ◽  
Theoretical Considerations ◽  
Single Enzyme

scholarly journals Function of the N-terminal propeptide of an aminopeptidase from Vibrio proteolyticus

2000 ◽  
Vol 350 (3) ◽  
pp. 671-676 ◽  
Author(s):  
Zhen-Zhong ZHANG ◽  
Satoru NIRASAWA ◽  
Yoshiaki NAKAJIMA ◽  
Michiteru YOSHIDA ◽  
Kiyoshi HAYASHI
Keyword(s):  
Escherichia Coli ◽  
Enzyme Activity ◽  
Active Region ◽  
Protein Expression ◽  
Inclusion Bodies ◽  
Active Enzyme ◽  
Vibrio Proteolyticus ◽  
Show Evidence ◽  
Inhibited Enzyme

An aminopeptidase from Vibrio proteolyticus was translated as a preproprotein consisting of four domains: a signal peptide, an N-terminal propeptide, a mature region and a C-terminal propeptide. Protein expression and analysis of the activity results demonstrated that the N-terminal propeptide was essential to the formation of the active enzyme in Escherichia coli. Urea dissolution of inclusion bodies and dialysis indicated that the N-terminal propeptide could facilitate the correct folding of the enzyme in vitro. Using l-Leu-p-nitroanilide as the substrate, the kinetic parameters (kcat and Km) of the pro-aminopeptidase and processed aminopeptidases were analysed. The results suggested that the N-terminal propeptide inhibited enzyme activity of the mature region. In contrast, the C-terminal propeptide did not show evidence of forming an active enzyme, of correctly folding in vitro or of inhibiting the active region.

Biochemical properties and kinetic parameters of dihydroxyphenyialanine – 5-hydroxytryptophan decarboxylase in brain, liver, and adrenals of cat

1979 ◽  
Vol 57 (7) ◽  
pp. 1014-1018 ◽  
Author(s):  
Sylvie Bouchard ◽  
Andrée G. Roberge
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Enzyme Activity ◽  
Kinetic Parameters ◽  
Biochemical Properties ◽  
Mechanisms Of Action ◽  
Decarboxylase Activity ◽  
Peripheral Organs ◽  
Exogenous Addition ◽  
The Central Nervous System

Biochemical properties and kinetic parameters of nonpurified dihydroxyphenylaianine –5-hydroxytryptophan decarboxylase extracted from brain and two peripheral organs, liver and adrenals, were studied in the cat. This study shows that decarboxylase activity in brain is lower than in peripheral organs and that 5-hydroxytryptophan can be decarboxylated without exogenous addition of pyridoxal-5′-phosphate (PLP). However, the addition of PLP substantially increases the enzyme activity. Excess of coenzyme (>60 μM) induces inhibition in adrenals and liver but not in the central nervous system (CNS). The observed inhibition might be related to the presence of a tetrahydroisoquinoline derivative formed in the medium. Differentiation between mechanisms of action of decarboxylase in the CNS and peripheral organs is suggested.

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