Enzyme studies on human and snail beta-mannosidase using a fluorescence assay and an HPLC/diode array method with Man beta (1-4)GlcNAc as substrate

1. Snail beta-mannosidase showed a Km value of 0.05 mM toward MU-beta-Man and could not be inhibited by Man, GlcNAc, Man beta(1-4)GlcNAc, Man beta(1-4)GlcNAc beta(1-N)urea or Man beta(1-4) GlcNAc beta(1-4)GlcNAc. 2. The Km value of the snail enzyme towards Man beta(1-4)GlcNAc, as measured by HPLC, was 10 mM, explaining the lack of inhibition. 3. The Km value of the human serum beta-mannosidase towards MU-beta-Man was 0.3 mM, but the human enzyme was not capable of degrading Man beta(1-4)GlcNAc in detectable amounts.

Diagnosis of medium-chain acyl-CoA dehydrogenase deficiency in lymphocytes and liver by a gas chromatographic method: the effect of oral riboflavin supplementation

The activity of medium-chain acyl-CoA dehydrogenase (MCAD) with octanoyl-CoA as a substrate was measured in human lymphocytes by a gas chromatographic technique. Phenazine methosulfate was used as the primary electron acceptor. After the addition of crotonase and subsequent hydrolysis, the reaction product 3-hydroxyoctanoic acid was quantitated by capillary gas-liquid chromatography of the trimethylsilyl derivatives. Control subjects had MCAD activities of 3.46 +/- 0.18 nmol/mg protein/min (n = 15). Five patients were investigated while receiving no therapy at all; MCAD activity ranged from 0.08 to 0.23 in four of them and was 0.65 in the fifth one. Subsequent to the long-term administration of 50-150 mg/d of riboflavin to MCAD-deficient patients (n = 11), these activities increased to an average of 0.41 in 10 patients and 2.22 in one. The activities in 15 obligate heterozygotes were 1.91 +/- 0.41 nmol/mg protein/min, thus enabling a clear distinction from controls. Neither heterozygotes nor a control responded to riboflavin. The method was also applicable to postmortem liver tissue. One patient, who had died suddenly and unexpectedly at the age of 19 mo, was correctly diagnosed as MCAD-deficient, whereas five additional children who died of the sudden infant death syndrome showed normal activities.

Medium- and long-chain 3-hydroxymonocarboxylic acids: analysis by gas chromatography combined with mass spectrometry

Medium- and long-chain 3-hydroxymonocarboxylic acids represent intermediates in the beta-oxidation of fatty acids: they accumulate in the plasma of patients with an inherited deficiency of long-chain 3-hydroxyacylcoenzyme A dehydrogenase. 3-Hydroxy acids with chain lengths varying from 6 to 16 were synthesized by a Reformatzky reaction. Capillary gas chromatography of the pertrimethylsilyl derivatives was performed on a CP-Sil 19 CB column, coupled to a quadrupole mass spectrometer in the electron impact mode. Calculation of the retention indices showed that the separation of the 3-hydroxy acids from the homologous straight-chain fatty acids may be troublesome, stressing the need for mass spectrometric identification.

3-Hydroxydicarboxylic aciduria due to long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency associated with sudden neonatal death: protective effect of medium-chain triglyceride treatment

Two siblings were found to be affected by long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency, one of which died suddenly and unexpectedly on the 3rd day of life suffering from extreme hypoketotic hypoglycaemia. The younger sibling started to have feeding problems, lowered consciousness, and liver dysfunction at the age of 5 months. Her urine contained large amounts of C6-C14 3-hydroxydicarboxylic acids and conjugated 3-hydroxyoctanoic acid, as verified by gas chromatography/mass spectrometry. Plasma long-chain acylcarnitine was increased. A clue to the diagnosis was given by the results of a phenylpropionic acid loading test. This revealed small, but significant amounts of conjugated 3-hydroxyphenylpropionic acid (phenylhydracrylic acid) in the patient's urine. Subsequently, the activity of long-chain 3-hydroxyacyl-CoA dehydrogenase was found to be deficient in cultured skin fibroblasts. Based on the findings obtained by a medium-chain triglyceride load, a diet enriched in this type of fat was prescribed. On this regimen the patient started to thrive, signs of cardiomyopathy disappeared, and her liver function normalized.

Molecular characterization of inherited medium-chain acyl-CoA dehydrogenase deficiency

Deficiency of medium-chain acyl-CoA dehydrogenase (MCAD) is a common inherited defect in energy metabolism. Characterization of the mRNA encoding MCAD in a Dutch MCAD-deficient patient revealed an A----G change at nucleotide position 985 of the MCAD mRNA coding region. This point mutation results in the substitution of a glutamic acid for a lysine at amino acid position 304 of the mature protein. The single base change was not found in any wild-type MCAD mRNAs. A mutant allele-specific oligonucleotide probe was used in a hybridization analysis of amplified genomic DNA of MCAD-deficient family members, a carrier, and normal individuals. The hybridization analysis specifically identified individuals who were heterozygotes or homozygotes. In addition to the point mutation, a significant proportion of the index patient's MCAD mRNA contained a variety of deletions and insertions as a result of exon skipping and intron retention. The missplicing occurred in multiple regions throughout the MCAD mRNA. Analysis of the patient's MCAD gene in the regions where the missplicing occurred most frequently did not reveal a mutation in the splicing acceptor or donor sites. Therefore, the molecular characterization of this family revealed a crucial point mutation in the MCAD gene and an unusual abnormality in MCAD pre-mRNA splicing.

Sialyl-alpha 2-6-mannosyl-beta 1-4-N-acetylglucosamine, a novel compound occurring in urine of patients with beta-mannosidosis

Human beta-mannosidosis urine was fractionated by gel permeation chromatography on Bio-Gel P-2 and by high performance liquid chromatography on Partisil 10 SAX. Besides the disaccharide Man beta 1-4GlcNAc as the major component, a sialic acid-containing compound was detected in an amount of 10% compared to that of Man beta 1-4GlcNAc. Structural characterization of the oligosaccharide and of its reduced analogue by sugar composition analysis, methylation analysis, gas-liquid chromatography-mass spectrometry, and 500-MHz 1H NMR spectroscopy gave conclusive evidence for a novel urinary constituent: NeuAc alpha 2-6Man beta 1-4GlcNAc. This linear trisaccharide can be considered as the result of an alpha 2-6-sialylation of the major accumulating compound, Man beta 1-4GlcNAc. The hitherto unknown linkage between sialic acid and mannose was shown to be susceptible to sialidase digestion.

O-phosphohydroxylysinuria: a new inborn error of metabolism?

An abnormal ninhydrin positive compound was observed in the urine of two unrelated patients with neurological abnormalities. The compound was isolated by cation exchange followed by preparative paper chromatography and finally purified via cation exchange column chromatography. Its identification as O-phosphohydroxylysine resulted from FAB mass spectrometry and NMR spectroscopy. Chemical synthesis confirmed the structure. It was tentatively postulated that these patients had a defect of the metabolism of hydroxylysine, viz., a deficiency of the enzyme O-phosphohydroxylysine phospholyase.

Accumulation of mannosyl-beta(1----4)-N-acetylglucosamine in fibroblasts and leukocytes of patients with a deficiency of beta-mannosidase

Cultured fibroblasts from two brothers with beta-mannosidosis were shown to accumulate the disaccharide mannosyl-beta(1----4)-N-acetylglucosamine in amounts of 52 and 68 nmol/mg protein. Structural identification of the Man beta(1----4)GlcNAc, isolated by HPLC, was performed by 500-MHz 1H-NMR spectroscopy and sugar composition analysis. Control fibroblasts did not contain a detectable amount of Man beta(1----4)GlcNAc. The disaccharide was also present in leukocytes from these patients, but not in controls, as could be demonstrated by thin-layer chromatography and sugar composition analysis. However, the amounts in leukocytes (5 and 6 nmol/mg protein) were much smaller than those in fibroblasts.

Stable isotope dilution analysis of succinylacetone using electron capture negative ion mass fragmentography: an accurate approach to the pre- and neonatal diagnosis of hereditary tyrosinemia type I

A sensitive and accurate isotope dilution assay using electron capture negative ion mass fragmentography was developed for succinylacetone in amniotic fluid, plasma and urine. The method utilizes (D4)-5(3)-methyl-3(5)-isoxasole propionic acid as internal standard. Sample pretreatment consisted of oximation at pH less than 2 to 5(3)-methyl-3(5)-isoxasole propionic acid, clean up using liquid partition chromatography and further derivatization to the pentafluorobenzyl ester. Control values in plasma revealed a mean means = 0.044 mumol/l, range = 0.005-0.163 mumol/l, in urine means = 0.15 mumol/l, range 0.01-0.40 mumol/l corresponding to means = 0.03 mumol/mmol creat., range 0.01-0.14 mumol/mmol creat., and in amniotic fluid means = 0.016 mumol/l, range = 0.001-0.030 mumol/l. The utility of the method was demonstrated by quantification of succinylacetone in urine from patients with hereditary tyrosinemia type I (n = 8, excretion range 2.60-493.3 mumol/l corresponding to 0.67-197.3 mumol/mmol creat.) and in two amniotic fluid samples from fetuses affected with this disorder (concentration of succinylacetone 0.085 and 1.50 mumol/l, respectively). Maternal urine from a woman carrying an affected fetus did not show elevated urinary succinylacetone excretion.

Urinary excretion of 2-methyl-2,3-butanediol and 2,3-pentanediol in patients with disorders of propionate and methylmalonate metabolism

Urine samples from patients with propionic acidemia and from a patient with methylmalonic acidemia contained unknown non-acidic metabolites by gas chromatography/mass spectrometry after ethyl acetate extraction. It could be demonstrated by mass spectrometric studies and by synthesis of reference compounds that the major metabolite was 2-methyl-2,3-butanediol, while smaller amounts of 2,3-pentanediol were also present. These diols were present in abnormal amounts in these patients during attacks of metabolic decompensation.

1,6-Anhydro-beta-D-glucopyranose (beta-glucosan), a constituent of human urine

When screening for abnormal urinary saccharides with one-dimensional thin-layer chromatography, an unknown component was observed in a position just above that of xylose. This compound was studied by gas chromatography-mass spectrometry and identified as the anhydro sugar beta-glucosan. It was observed in approximately 20% of all urine samples investigated by thin-layer chromatography. Excretory levels varied widely from zero up to 5.3 mmol/l. No correlation with age or disease could be established. The compound was thought to be of exogenous origin.

A 500-MHz 1H-n.m.r. study of oligosaccharides derived from gangliosides by ozonolysis-alkaline fragmentation

The structural-reporter-group resonances in the 1H-n.m.r. spectra of a series of ganglioside-derived oligosaccharides are completely assigned. The three different types of sialic acid residues which may occur in these compounds could be adequately characterized. They are distinguishable on the basis of the set of chemical shifts of their H-3a and H-3e atoms. The mutual influence of GalNAc beta-(1----4) and Neu5Ac alpha-(2----3), both linked to the same Gal residue, on the 1H-n.m.r. parameters of each other, reflects a well-defined solution conformation, which is held to be responsible for the resistance of this "internal" sialic acid towards various sialidases.

Octanoylglucuronide excretion in patients with a defective oxidation of medium-chain fatty acids

Octanoyl-beta-D-glucuronide was identified in the urine of five patients with hypoketotic hypoglycemia and dicarboxylic aciduria due to a defective beta-oxidation of medium-chain fatty acids. Two subjects who ingested large amounts of medium-chain triglycerides also excreted large amounts of the glucuronide. The substance was extracted from the urine with ethyl acetate and analyzed by: (1) gas chromatography/mass spectrometry (GC-MS) of the trimethylsilyl derivative and (2) preparative one-dimensional thin-layer chromatography followed by enzymatic hydrolysis with beta-glucuronidase and again GC-MS. A quantitative analysis was performed indirectly by measuring the urinary bound octanoate after the removal of octanoylcarnitine. Octanoylglucuronide represents an additional mechanism for the detoxification of octanoate; its formation may be of help for the maintenance of carnitine homeostasis in patients with medium-chain acyl-CoA dehydrogenase deficiency.