Roles of a 20 kDa protein associated with a carbocycle-forming enzyme involved in aminoglycoside biosynthesis in primary and secondary metabolism.

2-Deoxy-scyllo-inosose (DOI) synthase participates in the biosynthesis of 2-deoxystreptamine (DOS)-containing aminoglycoside antibiotics. The enzyme is expected to be of industrial use, because it converts a sustainable resource (glucose 6-phosphate) into carbocycle (DOI), which easily aromatizes to yield catechol. In the present study, we clarified the physiological role of a non-catalytic 20 kDa protein, BtrC2, associated with DOI synthase from the butirosin-producer Bacillus circulans. Based on the results of complementation analysis using btrC2 disruptant and western analysis against catalytic 40 kDa protein (BtrC) and BtrC2, it is suggested that BtrC2 has two functions. It is involved in the vitamin B(6) biosynthesis in primary metabolism, like homologous protein (Pdx2) in Bacillus subtilis. Additionally, it takes part in butirosin biosynthesis as stabilizer of DOI synthase by forming a heterodimer with BtrC, and qualifies B. circulans for stable and constant production of butirosin for long periods.

Expression analysis of the aldo-keto reductases involved in the novel biosynthetic pathway of tetrahydrobiopterin in human and mouse tissues.

Tetrahydrobiopterin (BH(4)) acts as a cofactor of the aromatic amino-acid hydroxylases, and its deficiency may result in hyperphenylalaninemia (HPA) and decreased production of the neurotransmitters. BH(4) is synthesized by sepiapterin reductase (SPR) from 6-pyruvoyl-tetrahydropterin (PPH(4)). A patient with SPR deficiency shows no HPA; however, an SPR knockout mouse exhibits HPA. We have reported on the SPR-unrelated novel biosynthetic pathway from PPH(4) to BH(4) (salvage pathway II) in which 3alpha-hydroxysteroid dehydrogenase type 2 and aldose reductase work in concert. In this study, we performed the expression analysis of both proteins in humans and wild-type mice. The results of expression analysis indicated that salvage pathway II worked in human liver; however, it did not act in human brain or in mouse liver and brain. For this reason, a patient with SPR deficiency may show progressive neurological deterioration without HPA, and SPR knockout mice may exhibit HPA and abnormal locomotion activity.

Molecular properties and tissue distribution of 30K proteins as ommin-binding proteins from diapause eggs of the silkworm, Bombyx mori.

We previously reported the purification of an ommin-binding protein (OMBP) from an acid-methanol extract of diapause eggs of the silkworm and that OMBP reacted with the anti-30K proteins antiserum. In order to clarify the relationship between OMBP and the 30K proteins, we attempted to determine the sequence of the N-terminal amino acid of OMBP, which was separated by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). We observed ten protein spots of various isoelectric points; the spots corresponded with 30 kDa. Based on the sequence of the N-terminal amino acid (20 residues), the spots belonged to two kinds of 30K proteins (6G1 and 19G1), which are known as the major plasma proteins in the larval hemolymph of the silkworm. The proteins are expected to attach to polysaccharide because they reacted with concanavalin A and elderberry bark lectin. Immunohistochemical observations clarified that the proteins were localized in yolk granules and serosa in the diapause egg. These results suggest that OMBP is composed of 30K proteins which were modified with polysaccharides. In addition, the expression of 30K proteins mRNA was observed at early embryonic stage in diapause eggs by RT-PCR analysis. The 30K proteins as OMBP may play an important role in the transport and accumulation of tryptophan metabolites and ommochrome during the formation of serosa.

Analysis of genes related to expression of aromatase and estradiol-regulated genes during sex differentiation in Xenopus embryos.

We analyzed the genes that exhibit transcriptional changes during sex differentiation in Xenopus, using fluorescent differential display (FDD). Search was then undertaken for sequences that were homologous to the differentially displayed DNA. In this report, trans-acting factors of activating transcription factor 4 (ATF 4) and heat shock proteins were selected, on the basis of homology, from candidate genes thought to be involved in the expression cascade of aromatase and estrogen receptor genes. The stage and tissue specificities and the effect of estradiol treatment on the expression of these genes were then examined using real-time quantitative polymerase chain reaction (RQ-RT-PCR). The expression of ATF 4, a member of the ATF/cAMP-responsive element-binding protein (CREB) family of genes, peaked in the gonads at stage 50 of development. Interestingly, expression of the genes encoding the heat shock cognate protein70. II (Hsc70. II) and the heat shock protein 70 (Hsp70) binding protein was strongly activated at stages 50 and 48 of development, respectively. The three genes revealed a higher transcription activity in the gonads than in other tissues. Although the expression of all of the genes encoding ATF 4, aromatase, Hsc70. II, and Hsp70 binding protein was activated in vitro by estrogen treatment, that of Hsc70. II and Hsp70 binding protein was found to be transient.

Tetrahydrobiopterin is synthesized from 6-pyruvoyl-tetrahydropterin by the human aldo-keto reductase AKR1 family members.

Tetrahydrobiopterin (BH(4)) is a cofactor for aromatic amino acid hydroxylases and nitric oxide synthase. The biosynthesis includes two reduction steps catalyzed by sepiapterin reductase. An intermediate, 6-pyruvoyltetrahydropterin (PPH(4)) is reduced to 1(')-oxo-2(')-hydroxypropyl-tetrahydropterin (1(')-OXPH(4)) or 1(')-hydroxy-2(')-oxopropyl-tetrahydropterin (2(')-OXPH(4)), which is further converted to BH(4). However, patients with sepiapterin reductase deficiency show normal urinary excretion of pterins without hyperphenylalaninemia, suggesting that other enzymes catalyze the two reduction steps. In this study, the reductase activities for the tetrahydropterin intermediates were examined using several human recombinant enzymes belonging to the aldo-keto reductase (AKR) family and short-chain dehydrogenase/reductase (SDR) family. In the reduction of PPH(4) by AKR family enzymes, 2(')-OXPH(4) was formed by 3 alpha-hydroxysteroid dehydrogenase type 2, whereas 1(')-OXPH(4) was produced by aldose reductase, aldehyde reductase, and 20 alpha-hydroxysteroid dehydrogenase, and both 1(')-OXPH(4) and 2(')-OXPH(4) were detected as the major and minor products by 3 alpha-hydroxysteroid dehydrogenases (types 1 and 3). The activities of aldose reductase and 3 alpha-hydroxysteroid dehydrogenase type 2 (106 and 35 nmol/mg/min, respectively) were higher than those of the other enzymes (0.2-4.0 nmol/mg/min). Among the SDR family enzymes, monomeric carbonyl reductase exhibited low 1(')-OXPH(4)-forming activity of 5.0 nmol/mg/min, but L-xylulose reductase and peroxisomal tetrameric carbonyl reductase did not form any reduced product from PPH(4). Aldose reductase reduced 2(')-OXPH(4) to BH(4), but the other enzymes were inactive towards both 2(')-OXPH(4) and 1(')-OXPH(4). These results indicate that the tetrahydropterin intermediates are natural substrates of the human AKR family enzymes and suggest a novel alternative pathway from PPH(4) to BH(4), in which 3 alpha-hydroxysteroid dehydrogenase type 2 and aldose reductase work in concert.

Molecular cloning and characterization of a cDNA encoding a novel cuticle protein in the silkworm, Bombyx mori.

We have cloned the full length of a novel cDNA named Bombyx mori cuticle protein that contains an AlaAlaProAla/Val-repeat (BMCPA) from a cDNA library of integument in the larval silkworm. Both a typical tandem repeat (A-A-P-A/V) for cuticle protein and a unique tandem repeat with Ser, Ala, Gly, Pro, Val, Tyr and Thr were observed in the predicted amino acid sequence of the cDNA encoding BMCPA. Approximately 80% of the amino acids in BMCPA were composed of Ser, Ala, Gly, Pro, Val and Tyr. Northern-hybridization analysis indicated that BMCPA mRNA is expressed only in the larval epidermis and that the expression pattern of the BMCPA gene in the developmental stage was observed mainly at the larval stage. We propose BMCPA may be a novel component of cuticle, and may play an important role in the integument of the larval silkworm.