A review of Hyphodiscaceae

In a recently published classification scheme for Leotiomycetes, the new family Hyphodiscaceae was erected; unfortunately, this study was rife with phylogenetic misinterpretations and hampered by a poor understanding of this group of fungi. This manifested in the form of an undiagnostic familial description, an erroneous familial circumscription, and the redescription of the type species of an included genus as a new species in a different genus. The present work corrects these errors by incorporating new molecular data from this group into phylogenetic analyses and examining the morphological features of the included taxa. An emended description of Hyphodiscaceae is provided, notes and descriptions of the included genera are supplied, and keys to genera and species in Hyphodiscaceae are supplied. Microscypha cajaniensis is combined in Hyphodiscus, and Scolecolachnum nigricans is a taxonomic synonym of Fuscolachnum pteridis. Future work in this family should focus on increasing phylogenetic sampling outside of Eurasia and better characterising described species to help resolve outstanding issues.

Update on Kleefstra Syndrome

Kleefstra syndrome is characterized by the core phenotype of developmental delay/intellectual disability, (childhood) hypotonia and distinct facial features. The syndrome can be either caused by a microdeletion in chromosomal region 9q34.3 or by a mutation in the euchromatin histone methyltransferase 1 (EHMT1) gene. Since the early 1990s, 85 patients have been described, of which the majority had a 9q34.3 microdeletion (>85%). So far, no clear genotype-phenotype correlation could be observed by studying the clinical and molecular features of both 9q34.3 microdeletion patients and patients with an intragenic EHMT1 mutation. Thus, to further expand the genotypic and phenotypic knowledge about the syndrome, we here report 29 newly diagnosed patients, including 16 patients with a 9q34.3 microdeletion and 13 patients with an EHMT1 mutation, and review previous literature. The present findings are comparable to previous reports. In addition to our former findings and recommendations, we suggest cardiac screening during follow-up, because of the possible occurrence of cardiac arrhythmias. In addition, clinicians and caretakers should be aware of the regressive behavioral phenotype that might develop at adolescent/adult age and seems to have no clear neurological substrate, but is rather a so far unexplained neuropsychiatric feature.

Pharmacokinetics of quercetin from quercetin aglycone and rutin in healthy volunteers

BACKGROUND

Quercetin is a flavonoid with a wide range of biological activities. It mainly occurs in plants as glycosides, such as rutin (quercetin rutinoside) in tea. Quercetin and rutin are used in many countries as vasoprotectants and are ingredients of numerous multivitamin preparations and herbal remedies.

OBJECTIVES

The primary objective was to characterise and compare the absorption and the pharmacokinetics of quercetin from quercetin aglycone and rutin. A secondary objective was to investigate which forms of quercetin are present in plasma.

METHODS

In this double blind, diet-controlled, two-period cross-over study, 16 healthy volunteers received three different doses of quercetin and rutin orally. The doses corresponded to 8 mg, 20 mg and 50 mg quercetin aglycone. Blood samples were obtained between 0 h and 32 h post-dose.

RESULTS

The overall kinetic behaviour of quercetin differed remarkably after ingestion of quercetin aglycone or rutin. The mean area under the plasma concentration-time curve from 0 h to 32 h [AUC(0-32)] and maximum plasma concentration (Cmax) values of the two treatments were similar. However, time to reach Cmax (tmax) was significantly shorter after the quercetin aglycone treatment than after the rutin treatment (1.9, 2.7 and 4.8 versus 6.5, 7.4 and 7.5 h, for doses 1, 2 and 3, respectively). Also, the absorption of quercetin from quercetin aglycone was predictable and inter-individual variation was small. In contrast, after ingestion of rutin, inter-individual variations in AUC(0-32) and Cmax values were considerable and seemed to be associated with gender and use of oral contraceptives. Quercetin and rutin were found in plasma as glucuronides and/or sulfates of quercetin and as unconjugated quercetin aglycone, but no rutin was detected.

CONCLUSIONS

In clinical trials, studying the effects of quercetin from rutin, bioavailability must be taken into consideration and plasma quercetin concentrations monitored. Whether our results apply to other glycosidic drugs as well, especially other rutosides, should be investigated.

Activation of chick tendon lysyl oxidase in response to dietary copper

Lysyl oxidase (EC 1.4.3.13), a cuproenzyme, can account for 10-30% of the copper present in connective tissue. Herein, we assess the extent to which tissue copper concentrations and lysyl oxidase activity are related because the functional activity of lysyl oxidase and the copper content of chick tendon are both related to dietary copper intake. Chicks (1-d old) were fed diets (basal copper concentration, 0.4 microg/g diet) to which copper was added from 0 to 16 microg/g diet. Liver and plasma copper levels tended to normalize in chickens that consumed from 1 to 4 microg copper/g of diet, whereas tendon copper concentrations suggested an unusual accumulation of copper in chickens that consumed 16 microg copper/g diet. The molecular weight of lysyl oxidase was also estimated using matrix-assisted laser desorption ionization/time-of-flight/mass spectrometry (MALDI/TOF/MS). A novel aspect of these measurements was estimation of protein mass directly from the surface of chick tendons and aortae. Whether copper deficiency (0 added copper) or copper supplementation (16 microg copper/g of diet) caused changes in the molecular weight of protein(s) in tendon corresponding to lysyl oxidase was addressed. The average molecular weight of the peak corresponding to lysyl oxidase in tendon and aorta from copper-deficient birds was 28,386 Da +/- 86, whereas the average molecular weight of corresponding protein in tendon from copper-supplemented birds was 28,639 Da +/- 122. We propose that the shift in molecular weight is due in part to copper binding and the formation of lysyl tyrosyl quinone, the cofactor at the active site of lysyl oxidase.

Cloning and characterization of a third human lysyl hydroxylase isoform

Lysyl hydroxylase (EC 1.14.11.4), a homodimer, catalyzes the formation of hydroxylysine in collagens. Recently, an isoenzyme termed lysyl hydroxylase 2 has been cloned from human sources [M. Valtavaara, H. Papponen, A.-M. Pirttilä, K. Hiltunen, H. Helander and R. Myllylä (1997) J. Biol. Chem. 272, 6831-6834]. We report here on the cloning of a third human lysyl hydroxylase isoenzyme, termed lysyl hydroxylase 3. The cDNA clones encode a 738 amino acid polypeptide, including a signal peptide of 24 residues. The overall amino acid sequence identity between the processed human lysyl hydroxylase 3 and 1 polypeptides is 59%, and that between the processed lysyl hydroxylase 3 and 2 polypeptides is 57%, whereas the identity to the processed Caenorhabditis elegans polypeptide is only 45%. All four recently identified critical residues at the catalytic site, two histidines, one aspartate, and one arginine, are conserved in all these polypeptides. The mRNA for lysyl hydroxylase 3 was found to be expressed in a variety of tissues, but distinct differences appear to exist in the expression patterns of the three isoenzyme mRNAs. Recombinant lysyl hydroxylase 3 expressed in insect cells by means of a baculovirus vector was found to be more soluble than lysyl hydroxylase 1 expressed in the same cell type. No differences in catalytic properties were found between the recombinant lysyl hydroxylase 3 and 1 isoenzymes. Deficiency in lysyl hydroxylase 1 activity is known to cause the type VI variant of the Ehlers-Danlos syndrome, and it is therefore possible that deficiency in lysyl hydroxylase 3 activity may lead to some other variant of this syndrome or to some other heritable connective tissue disorder.

Copper, lysyl oxidase, and extracellular matrix protein cross-linking

Protein-lysine 6-oxidase (lysyl oxidase) is a cuproenzyme that is essential for stabilization of extracellular matrixes, specifically the enzymatic cross-linking of collagen and elastin. A hypothesis is proposed that links dietary copper levels to dynamic and proportional changes in lysyl oxidase activity in connective tissue. Although nutritional copper status does not influence the accumulation of lysyl oxidase as protein or lysyl oxidase steady state messenger RNA concentrations, the direct influence of dietary copper on the functional activity of lysyl oxidase is clear. The hypothesis is based on the possibility that copper efflux and lysyl oxidase secretion from cells may share a common pathway. The change in functional activity is most likely the result of posttranslational processing of lysyl oxidase. Copper is essential for organic cofactor formation in amine oxidases such as lysyl oxidase. Copper-containing amine oxidases have peptidyl 2,4,5 tri(oxo)phenylalanine (TOPA) at their active centers. TOPA is formed by copper-catalyzed oxidation of tyrosine, which takes place as part of Golgi or trans-Golgi processing. For lysyl oxidase, recent evidence (Science 1996;273:1078-84) indicates that as an additional step, a lysyl group at the active center of lysyl oxidase reacts with TOPA or its precursor to form lysyl tyrosylquinone.

Incorporation of copper into lysyl oxidase

Lysyl oxidase is a copper-dependent enzyme involved in extracellular processing of collagens and elastin. Although it is known that copper is essential for the functional activity of the enzyme, there is little information on the incorporation of copper. In the present study we examined the insertion of copper into lysyl oxidase using 67Cu in cell-free transcription/translation assays and in normal skin fibroblast culture systems. When a full-length lysyl oxidase cDNA was used as a template for transcription/translation reactions in vitro, unprocessed prolysyl oxidase appeared to bind copper. To examine further the post-translational incorporation of copper into lysyl oxidase, confluent skin fibroblasts were incubated with inhibitors of protein synthesis (cycloheximide, 10 microg/ml), glycosylation (tunicamycin, 10 microg/ml), protein secretion (brefeldin A, 10 microg/ml) and prolysyl oxidase processing (procollagen C-peptidase inhibitor, 2.5 microg/ml) together with 300 microCi of carrier-free 67Cu. It was observed that protein synthesis was a prerequisite for copper incorporation, but inhibition of glycosylation by tunicamycin did not affect the secretion of 67Cu as lysyl oxidase. Brefeldin A inhibited the secretion of 67Ci-labelled lysyl oxidase by 46%, but the intracellular incorporation of copper into lysyl oxidase was not affected. In addition, the inhibition of the extracellular proteolytic processing of prolysyl oxidase to lysyl oxidase had minimal effects on the secretion of protein-bound 67Cu. Our results indicate that, similar to caeruloplasmin processing [Sato and Gitlin (1991) J. Biol. Chem. 266, 5128-5134], copper is inserted into prolysyl oxidase independently of glycosylation.

Modulation of lysyl oxidase by dietary copper in rats

Lysyl oxidase levels were estimated in rat tissues using an enzyme-linked immunosorption assay (ELISA) and a functional assay standardized against known amounts of purified lysyl oxidase. High concentrations of lysyl oxidase (> or = 150 micrograms/g of tissue or packed cells) were detected in connective tissues, such as tendon and skin. Values for aorta, kidney, lung and liver ranged from 30 to 150 micrograms/g of tissue; values for skeletal muscle and diaphragm were < 30 micrograms/g tissue. Purified rat skin lysyl oxidase catalyzed the release of 50-100 Bq of tritium per micrograms enzyme in assays that used 3H-elastin-rich substrates. In dense connective tissues, good agreement was obtained for the values from ELISA and those derived from measurements of functional activity in aorta, lung, skin and tendon (r2 > 0.9). When egg white-based experimental diets containing 2 or 10 micrograms/g added copper were fed to weanling rats, values for skin lysyl oxidase functional activity in the group fed 2 micrograms/g added copper were one-third to one-half the values for skin lysyl oxidase functional activity in rats fed 10 micrograms/g copper. This reduction in lysyl oxidase activity, however, had minimal effect on indices of collagen maturation in rat skin, e.g., collagen solubility in neutral salt and dilute acid or the levels of acid stable cross-links. Moreover, copper deficiency did not influence the steady-state levels of lysyl oxidase specific mRNA in rat skin or the apparent amounts of lysyl oxidase in rat skin as determined by ELISA. These observations underscore that the concentration of lysyl oxidase is relatively high in dense corrective tissues, and although decreasing dietary copper influences functional activity, there is little apparent effect on the production of lysyl oxidase protein.

Expression and accumulation of lysyl oxidase, elastin, and type I procollagen in human Menkes and mottled mouse fibroblasts

Menkes syndrome in humans is an X-linked disorder characterized in part by abnormal copper transport, cellular copper sequestration, and defective crosslinking of collagen and elastin. A decrease in the functional activity of lysyl oxidase, a cuproenzyme, is thought in part to be responsible for the decreased crosslinking of collagen and elastin. It has also been suggested that low levels of lysyl oxidase activity may occur secondarily to disturbances in intracellular copper translocation and consequently impaired incorporation of copper into lysyl oxidase. Herein, we examine the expression and accumulation of selected extracellular matrix proteins in fibroblasts from a Menkes patient, as well as fibroblasts from the tortoiseshell (MoTo/y) mouse. The MoTo mutation is an allele of the mottled (Mo) locus, which is considered to be a murine analog of the human Menkes locus. In both Menkes and tortoiseshell fibroblasts, levels of lysyl oxidase mRNA transcripts were less than 15% of levels for corresponding controls. The level of elastin mRNA transcripts was also markedly lower in both cell lines in comparison to controls. In contrast, the levels of procollagen Type I mRNA were similar or enhanced in Menkes and MoTo/y fibroblasts compared to their respective controls. Consequently, we conclude that the connective tissue defects associated with Menkes syndrome and those occurring in mottled mouse mutants involve more than abnormal copper utilization in the formation of lysyl oxidase holoenzyme. Based on the present studies in cell culture, the production of essential enzymes and matrix proteins, such as lysyl oxidase and elastin, appear to be altered at the level of transcription or mRNA turnover.