scholarly journals H.p.l.c. of oligo(sialic acids). Application to the determination of the minimal chain length serving as exogenous acceptor in the enzymic synthesis of colominic acid

1991 ◽  
Vol 280 (3) ◽  
pp. 575-579 ◽  
Author(s):  
M A Ferrero ◽  
J M Luengo ◽  
A Reglero
Keyword(s):  
Chain Length ◽  
Complete Separation ◽  
Sialic Acids ◽  
Degree Of Polymerization ◽  
Direct Transfer ◽  
Maximal Rate ◽  
Colominic Acid ◽  
Membrane Bound

A rapid, sensitive and easy h.p.l.c. method was developed for the quantitative analysis of oligosialic acids. This procedure which permits the complete separation (in 23 min) of several sialyloligomers with a degree of polymerization of between 1 and 16, has been employed to establish the minimal chain length of oligomer accepted, as an exogenous acceptor, by Escherichia coli K-235 sialytransferase complex (ST) leading to the synthesis in vitro of colominic acid. We showed that this membrane-bound enzyme catalyses the direct transfer of Neu5Ac residues (one by one) from CMP-Neu5Ac to an exogenous acceptor molecule which contains at least three Neu5Ac residues. Free Neu5Ac or (Neu5Ac)2 were not recognized as substrates, whereas the maximal rate of polymer elongation was achieved when (Neu5Ac)5 was used as substrate.

Pharmacokinetics of thyrotrophin-releasing hormone in patients in different thyroid states

1991 ◽  
Vol 128 (1) ◽  
pp. 153-159 ◽  
Author(s):  
E. Iversen
Keyword(s):  
Thyroid Hormones ◽  
Half Life ◽  
Thyrotrophin Releasing Hormone ◽  
Tissue Degradation ◽  
The Central Nervous System ◽  
Membrane Bound ◽  
Hormone Control ◽  
Hypothyroid Patients

ABSTRACT In view of recent reports suggesting that thyroid hormone control of TRH degradation occurs outside the central nervous system in animals, the effect of thyroid status on serum and tissue degradation of TRH in man was investigated. In six patients with hyperthyroidism and six patients with hypothyroidism, constant TRH infusions were carried out for determination of plasma clearance rate (PCR) and half-life of disappearance (t½) of TRH, with simultaneous determination of half-life of disappearance in serum in vitro (t½p). Using a kinetic model, this enabled the calculation of the half-life of disappearance in the extravascular tissue compartment (t½t). All patients were reinvestigated after they had become euthyroid. PCR, t½ and t½p were 22·1 ±3·4 ml/kg per min, 6·8±1·1 min and 17·3±6·7 min (means ± s.d.) respectively in the euthyroid patients. The t½p was slightly but significantly prolonged during hyperthyroidism. The t½ was 5·6 min in the hyperthyroid patients compared with 9·4 min in the hypothyroid patients. The calculated t½t was 6·5 min in the euthyroid patients. In the patients with untreated hyperthyroidism, t½t was significantly reduced (22·7±10·7%; mean ± s.d.), while it was considerably prolonged (41·1±24·6%) in patients with untreated hypothyroidism. The percentage reduction or prolongation of t½t was negatively correlated with the logarithm of the serum concentrations of thyroxine (r = 0·92) and tri-iodothyronine (r= 0·91) in the untreated patients. Thus, thyroid hormones induce alterations in the pharmacokinetics of TRH. This may partly be due to induction by thyroid hormones of membrane-bound pyroglutamyl aminopeptidase. Journal of Endocrinology (1991) 128, 153–159

scholarly journals Limited Hydrolysis of Polysialic Acid by Human Neuraminidase Enzymes

2021 ◽  
Author(s):  
Carmanah D. Hunter ◽  
Christopher Cairo
Keyword(s):  
Polysialic Acid ◽  
Chemical Properties ◽  
Sialic Acids ◽  
Degree Of Polymerization ◽  
Health And Disease ◽  
Substrate Tolerance ◽  
The Impact ◽  
Hydrolysis Of ◽  
Unique Chemical

Regulation of sialic acids by human neuraminidase (hNEU) enzymes is important to many biological processes. Defining hNEU substrate tolerance can help to elucidate the roles of these enzymes in regulating sialosides in human health and disease. Polysialic acid (polySia) is a polyanion of α(2→8) linked sialic acids with roles in nervous, reproductive, and immune systems and is dysregulated in some malignancies and mental disorders. The unique chemical properties of this polymer, which include an enhanced susceptibility to acid-catalyzed hydrolysis, have hampered its study. Herein we describe the first<i> </i>systematic study of hNEU isoenzyme activity towards polysialic acid <i>in vitro.</i> The experimental design allowed us to study the impact of several factors that may influence polysialic acid degradation including pH, polymer size, and the relative ionic strength of the surrounding media. We report that short chains of polysialic acid (degree of polymerization, DP 3-8) were substrates of NEU3 and NEU4 at acidic pH, but not at neutral pH. No hNEU-catalyzed hydrolysis of longer polymers (DP 10-20) was detected. These findings suggest a neuraminidase-independent mechanism for polysialic acid turnover such as internalization and degradation in endosomes and lysosomes.

De novo synthesis of fructo-oligosaccharides in leaf disks of certain Asteraceae

1972 ◽  
Vol 50 (2) ◽  
pp. 295-303 ◽  
Author(s):  
K. R. Chandorkar ◽  
F. W. Collins
Keyword(s):  
Chain Length ◽  
De Novo ◽  
Close Correlation ◽  
Acid Synthesis ◽  
Degree Of Polymerization ◽  
De Novo Synthesis ◽  
The Relationship ◽  
Leaf Disks

Incubation of leaf disks of certain genera of Asteraceae on phosphate-buffered, 5% sugar solutions resulted in the de novo synthesis of a homologous series of inulin-type fructosans. Fructo-oligosaccharides of degree of polymerization 3 to 21 or 22 were present in dandelion, chicory, lettuce, hawkweed, and sow thistle leaf disks after 72 h, but not in dahlia or sunflower. Synthesis occurred with media containing either fructose, glucose, or sucrose, but not with mannose or galactose. Fructosan formation began after about 36 h and continued with the sequential synthesis of homologs of increasing chain length. After 72 h, the relationship between the amount of polymer synthesized and the chain length appeared to be logarithmically biphasic, consisting of two series of exponentially decreasing values. Incubation for 120 h however, resulted in a distribution more closely resembling that found naturally in fructosan storing tissues. 14C-tracer studies showed that both the endogenous and exogenous carbohydrate sources contribute to fructosan synthesis. Fructo-oligosaccharide formation was blocked by cycloheximide, puromycin, and actinomycin D but not chloramphenicol, indicating that cytoplasmic protein and nucleic acid synthesis was required. Analysis of fructosan formation during incubation suggests a close correlation between transfructosylation mechanisms observed in vitro and the de novo synthesis of fructosans in vivo.

scholarly journals Limited Hydrolysis of Polysialic Acid by Human Neuraminidase Enzymes

2021 ◽  
Author(s):  
Carmanah D. Hunter ◽  
Christopher Cairo
Keyword(s):  
Polysialic Acid ◽  
Chemical Properties ◽  
Sialic Acids ◽  
Degree Of Polymerization ◽  
Health And Disease ◽  
Substrate Tolerance ◽  
The Impact ◽  
Hydrolysis Of ◽  
Unique Chemical

Regulation of sialic acids by human neuraminidase (hNEU) enzymes is important to many biological processes. Defining hNEU substrate tolerance can help to elucidate the roles of these enzymes in regulating sialosides in human health and disease. Polysialic acid (polySia) is a polyanion of α(2→8) linked sialic acids with roles in nervous, reproductive, and immune systems and is dysregulated in some malignancies and mental disorders. The unique chemical properties of this polymer, which include an enhanced susceptibility to acid-catalyzed hydrolysis, have hampered its study. Herein we describe the first<i> </i>systematic study of hNEU isoenzyme activity towards polysialic acid <i>in vitro.</i> The experimental design allowed us to study the impact of several factors that may influence polysialic acid degradation including pH, polymer size, and the relative ionic strength of the surrounding media. We report that short chains of polysialic acid (degree of polymerization, DP 3-8) were substrates of NEU3 and NEU4 at acidic pH, but not at neutral pH. No hNEU-catalyzed hydrolysis of longer polymers (DP 10-20) was detected. These findings suggest a neuraminidase-independent mechanism for polysialic acid turnover such as internalization and degradation in endosomes and lysosomes.

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