Tryptophan residues and the sugar binding site of potato lectin

Potato lectin (Solanum tuberosum agglutinin, STA) was found to contain fluorescent tryptophan residues highly exposed to solvent. The binding of chitin oligosaccharides to STA induced fluorescence quenching, a shift of the fluorescence maximum to shorter wavelength, a decrease in the quenching constant of iodide ion and a decrease of the number of tryptophan residues modifiable by N-bromosuccinimide. The results suggested that one tryptophan residues is located at or near a sugar binding site of STA, and that its environment is altered from hydrophilic to relatively more hydrophobic upon interaction with specific sugars. The binding constants of STA with chitin oligosaccharides were determined by measuring the peak-trough heights in the fluorescence difference spectra induced by various concentrations of sugars. The inhibition constants of chitin oligosaccharides for the hemagglutinating activity of STA were obtained by the method of Pitts and Yang [(1981) Biochem. J. 195, 435-439] and the results were in good agreement with those obtained by the fluorescence spectral method. Standard and unitary free energy changes (delta G0 and delta Gu) and standard enthalpy changes (delta H0) were also obtained. These values decreased with sugar chain length up to at least the tetramer. Thus, it was assumed that there are at least 4 subsites, A, B, C, and D, in the sugar binding site of STA. The contributions to the binding energy (delta Gu) were -17.0, -12.6, -7.3, and -4.4 kJ/mol at subsites A, B, C, and D, respectively, and the bindings of chitin monomer (GlcNAc), dimer, trimer, and tetramer were assumed to occur at subsite A, AB, ABC, and ABCD, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding of fibronectin and its proteolytic fragments to glycosaminoglycans. Exposure of cryptic glycosaminoglycan-binding domains upon limited proteolysis

Binding of intact plasma fibronectin and its proteolytic fragments to glycosaminoglycans immobilized on agarose beads was systematically compared at different ionic strengths. In low ionic strength buffer, intact fibronectin bound to heparin and high sulfated heparan sulfate, but not to low sulfated heparan sulfate, dermatan sulfate, chondroitin sulfates A and C, or hyaluronic acid. Fractionation of the thermolysin digest of fibronectin on the glycosaminoglycan-Sepharoses at low ionic strength revealed that three groups of fragments, i.e. Mr = 150,000-140,000, 24,000, and 16,000 (150K-140K, 24K, and 16K) fragments, were capable of binding to glycosaminoglycans with different specificities and affinities. The 150K-140K fragments exhibited the same specificities as intact fibronectin, binding only to heparin and high sulfated heparan sulfate. However, the 24K fragment bound not only to these two glycosaminoglycans but also to low sulfated heparan sulfate and other glycosaminoglycans as well. The 16K fragments were also capable of binding to most glycosaminoglycans with lower affinity than the 24K fragment. These results suggest that the binding sites in the 24K and 16K fragments are cryptic in the intact protein, but are exposed after limited proteolysis. The binding of fibronectin and its fragments to glycosaminoglycans is dependent on the ionic strength. At physiologic ionic strength, only heparin-Sepharose could bind intact fibronectin. Similarly, only heparin-Sepharose could bind the 150K-140K and 24K fragments, but not the 16K fragments, at the same ionic condition. Other glycosaminoglycan-Sepharoses did not retain significant amounts of any of the fibronectin fragments, suggesting that the affinity of plasma fibronectin and its fragments to heparan sulfate and other glycosaminoglycans, except heparin, is not strong enough to achieve stable mono- (or di-) valent binding under physiologic conditions.

Identification of 3-hydroxy-3-ethylglutaric acid in urine of patients with propionic acidaemia

By gas chromatographic mass spectrometric analysis, 3-hydroxy-3-ethylglutaric acid was identified in the urine of patients with propionyl CoA carboxylase deficiency. Simultaneously, large amounts of 3-hydroxyvaleric acid and 3-oxovaleric acid, as well as a number of metabolites previously well known in this disorder, were also found in the urine of the patients. It is suggested that formation of 3-oxovaleric acid and 3-hydroxyvaleric acid proceeds via 3-hydroxy-3-ethylglutaryl CoA as an intermediate by a mechanism similar to that of ketone body formation.

Purification and characterization of two types of Cytisus multiflorus hemagglutinin by affinity chromatography

Two hemagglutinins were separated from extracts of Cytisus multiflorus seeds by successive affinity chromatographies on columns of galactose- and di- N-acetylchitobiose-Sepharose 4B. One was found to be inhibited by di- N-acetylchitobiose or tri- N-acetylchitotriose and shown to possess anti-H(O) activity [Cytisus-type anti-H(O) hemagglutinin designated as Cytisus multiflorus hemagglutinin I]. The other, which was not a blood group-specific hemagglutinin, was inhibited by galactose or lactose (hemagglutinin II). Hemagglutinins I and II were further purified by gel filtration on Sephacryl S-300. These preparations were homogeneous as judged by polyacrylamide gel electrophoresis and gel filtration. The molecular weights of the purified hemagglutinins I and II were found to be 86000 by sedimentation equilibrium analysis and 80000 by gel filtration. On disc gel electrophoresis in the presence of sodium dodecyl sulfate and dithiothreitol, both hemagglutinins gave a single component of a molecular weight of 42000 +/- 2000, suggesting that these hemagglutinins are dimeric proteins of two identical subunits. Hemagglutinins I and II contain 2.7% and 1.5% carbohydrate, respectively, and only very small amounts of cystine and methionine were detected, but they are rich in aspartic acid and serine. Treatment of human O erythrocytes with a purified H-decomposing enzyme (alpha-L-fucosidase from Bacillus fulminans abolished the agglutinability of the cells with hemagglutinin I. This indicates that the L-fucosyl residue is important even for the H-specificity detected by this di-N-acetylchitobiose-specific hemagglutinin I.

Studies of urinary organic acid profiles of a patient with dihydrolipoyl dehydrogenase deficiency

Using gas chromatography-mass spectrometry (GC/MS), urinary organic acid profile studies were carried out on a patient with dihydrolipoyl dehydrogenase (E3) deficiency. Elevated levels of 2-hydroxyglutaric acid, 2-hydroxyisocaproic acid and 2-oxoisocaproic acid were observed in addition to lactic acid, 2-oxoglutaric acid, 2-hydroxyisovaleric acid and 2-hydroxybutyric acid previously described in patients with E3 deficiency. The 2-oxoglutaric acid levels were significantly lowered after branched-chain amino acid restriction. In an acute period, the patient was slightly ketoacidotic and excreted larger amounts of 2-oxoglutaric acid and lactic acid than in a static period. It was shown that, prior to confirmatory enzyme studies, patients with E3 deficiency who were suspected to have atypical maple syrup urine disease or chronic lactic acidosis can be rapidly identified by GC/MS analysis of urinary acids.

Purification and characterization of potato lectin

Potato lectin (Solanum tuberosum agglutinin, STA), purified by affinity chromatography on tri-N-acetylchitotriose-Sepharose 6B, has Mr approximately 100,000, as estimated by gel filtration on Sephadex G-150 and is an aggregating system with a monomer Mr = 54,000, as estimated by sedimentation equilibrium analysis. Equilibrium dialysis showed that STA (dimer) has two binding sites for a specific sugar per molecule. STA has a high content of sugar, most of which is L-arabinose, and is rich in Hyp and Cys. On interaction with specific sugars, STA induced a UV difference spectrum having positive peaks at 292 and 285 nm characteristic of tryptophyl residues. The association constants with chitin oligosaccharides, determined from the intensities of the difference spectra at various concentrations of sugars, increased with increasing chain length of the sugar. Association constants obtained by frontal affinity chromatography of chitin oligosaccharides with STA-Sepharose were in good agreement with those obtained by difference spectra, whereas the association constants obtained by frontal affinity chromatography of STA with di- and tri-N-acetylchitotriose-Sepharose were much higher, presumably owing to the effect of multivalency of ligands. The CD spectra of STA in the far UV region indicate the presence of 40% of beta- and 60% of unordered form, and no alpha-helix conformation, which supports the structure suggested by the amino acid composition and the high content of sugar.

Immunochemical and spectral studies on Vicia faba agglutinin

Affinity chromatographic purification of Vicia faba agglutinin (VFA) was performed with a Sephadex G-150 column according to the method of Allen and Johnson [Biochim. Biophys. Acta (1976)]. VFA has 10 tryptophanyl residues per molecule on the assumption that its molecular weight is 50,000 daltons. Equilibrium dialysis with methyl a-D-[glucose-14C(U)]glucopyranoside showed that VFA has two sugar binding sites per molecule with a binding constant of 220 M-1. Upon interaction with specific sugars, VFA induced UV-difference spectra which are typical of the perturbation of tryptophanyl residues. Therefore, the binding constants of VFA with specific sugars could be calculated from the intensity changes in the difference spectra induced by various concentrations of the sugars. The results obtained were in good agreement with the results of hemagglutination inhibition assays. 3-O-Methyl-D-glucose had the highest binding constant (1.9 x 10(3) M-1) among the sugars examined. The binding constants of VFA with glucose, mannose, methyl a-D-glucopyranoside, methyl a-D-mannopyranoside, and maltose were 290, 900, 220, 500, and 220 M-1, respectively, which are lower than those of concanavalin A. VFA did not bind with mucopolysaccharides containing 2-acetamide-2-deoxy-a-, or -beta-D-glucopyranosyl residues, such as heparin, heparan sulfate, and hyaluronic acid. The far UV-CD spectrum of VFA was similar to that of concanavalin A.

Fluorescence spectral studies on the specific interaction between sulfated glycosaminoglycans and potato lectin

On excitation at 280 nm, Solanum tuberosum agglutinin (STA) produced a fluorescence emission spectrum with a maximum at 347 nm, which is typical of tryptophanyl residues. The fluorescence emission maximum was shifted toward shorter wavelength and quenched by the addition of specific sugars. The changes were analyzed precisely and quantitatively by measuring the fluorescence difference spectra. This method required far smaller amounts of samples than UV-difference spectroscopy to obtain the binding parameters. The binding constants of chitin sulfate, keratan sulfate, and highly sulfated keratan sulfate were calculated to be 1.8 X 10(5) M-1, 3.4 X 10(5) M-1, and 5.2 X 10(5) M-1, respectively. The results indicate that consecutive and non-consecutive, alternating (1 leads to 4)-N-acetyl-beta-D-glucosaminyl residues in the glycosaminoglycans can interact freely with STA in spite of the existence of the sulfate groups at C-6 of the N-acetyl-D-glucosaminyl residues and extra sulfate groups at C-6 of the galactosyl residues linked with N-acetyl-6-O-sulfo-beta-D-glucosamine.

Four-hydroxyphenylpyruvic acid oxidase deficiency with normal fumarylacetoacetase: a new variant form of hereditary hypertyrosinemia

Enzymatic studies on the liver of an infant are described-a case of hypertyrosinemia without hepatic dysfunction. His parents were siblings and the mother had hypertyrosinemia. Excessive amounts of 4-hydroxyphenylpyruvic acid (pHPP), 4-hydroxyphenylacetic acid (pHPL), and 4-hydroxyphenylacetic acid (pHPA) were found to be excreted in the patient's urine as well as in the urine of the mother and the inhibitor of porphobilinogen synthetase was not found. Soluble tyrosine aminotransferase (s-TAT), separated from that of the mitochondrial form (m-TAT) by DE 52 column chromatography, was normal in the patient's liver, both quantitatively and qualitatively. The activities of fumarylacetoacetase in the patient's liver and in the peripheral leucocytes from the parents were normal. The activity of pHPP oxidase in the patient's liver was approximately 5% of the control and the enzyme had a high Km value for pHPP (controls: 0.06 +/- 0.01 mM, patient: 0.23 +/- 0.03 mM). From these results, the patient was thought to be different from previously described types of tyrosinemia and perhaps representative of a new variant form. This is the first report concerning 4-hydroxyphenylpyruvic acid oxidase deficiency alone. Mild metal retardation and mild hypertyrosinemia may be offered as typical clinical features of the disease.

Modification by Su-10'603 of the response to histamine on the production of cortisol and corticosterone in isolated canine adrenocortical cells

The effect of Su-10'603 on the cortisol and corticosterone response to histamine in dispersed canine adrenocortical cells was examined. The production of cortisol and corticosterone in isolated dog adrenocortical cell incubations increased in a dose-dependent manner at concentrations of histamine between 0.01 and 10.0 micrograms/ml medium, with the predominant production of cortisol. When Su-10'603 (0.005 to 5.0 micrograms/ml medium), an inhibitor of 17 alpha-hydroxylation on corticosteroidogenesis, was added in cell incubations with histamine (1.0 micrograms/ml medium), the production of cortisol decreased in a reciprocal fashion, with a concomitant increase of corticosterone production. At the concentration between 0.05 and 0.1 microgram Su-10'603/ml medium, there was a shift from cortisol to corticosterone as the predominant product. These results indicate that in the dog, histamine at pathophysiological concentration stimulates steroidogenesis and acts at a relatively early stage in the biosynthetic pathway.