~~ ~Aldehyde oxidase (AO; EC 1.2.3.1) that could oxidize indole-3-acetaldehyde into indole-3-acetic acid was purified approximately 2000-fold from coleoptiles of 3-d-old maize (Zea mays 1.) seedlings. The apparent molecular mass of the native enzyme was about 300 kD as estimated by gel-filtration column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the enzyme was composed of 150-kD subunits. It contained flavin adenine dinucleotide, iron, and molybdenum as prosthetic groups and had absorption peaks in the visible region (300-600 nm). To our knowledge, this is the first demonstration of the presence of flavin adenine dinucleotide and metals i n plant AO. Other aromatic aldehydes such as indole-3-aldehyde and benzaldehyde also served as good substrates, but N-methylnicotinamide, a good substrate for animal AO, was not oxidized. 2-Mercaptoethanol, p-chloromercuribenzoate, and iodoacetate partially inhibited the activity, but well-known inhibitors of animal AO, such as menadione and estradiol, caused no reduction in activity. These results indicate that, although maize AO is similar to animal enzymes in molecular mass and cofactor components, it differs i n substrate specificity and susceptibility t o inhibitors. lmmunoblotting analysis with mouse polyclonal antibodies raised against the purified maize AO showed that the enzyme was relatively rich i n the apical region of maize coleoptiles. The possible role of this enzyme is discussed in relation to phytohormone biosynthesis in plants.AO (EC 1.2.3.1) has been extensively investigated in animals and microorganisms. The enzyme catalyzes the oxidation of a variety of aldehydes and N,-containing heterocycles in the presence of.0, or certain redox dyes (Rajagopalan and Handler, 1966; Hall and Krenitsky, 1986). The enzyme has also been reported to reduce diphenyl sulfoxides (Yoshihara and Tatsumi, 1986), aromatic heterocyclic compounds (Bauer and Howard, 1991), and oximes (Tatsumi and Ishigai, 1987). AO is similar t o xanthine dehydrogenase (oxidase) in being a multicomponent enzyme that contains a molybdenum cofactor, nonheme iron, and FAD as prosthetic groups. The enzyme is found in the small intestine and liver of animals and has been implicated in the detoxification of various xenobiotics, including certain cancer chemotherapeutic agents (Bauer and Howard, 1991;Stoddart and Levine, 1992; Hirao et al., 1994). The enzyme may also play a role in retinoic acid synthesis (Tomita et al., 1993; Huang and Ichikawa, 1994) and in the degradation of aromatic aldehydes formed as a result of lignin breakdown by a soil bacterium (Crawford et al., 1982) and snails (Large and Connock, 1994).However, in plants only a limited amount of information has been published concerning this enzyme, including studies of Auena coleoptiles (Rajagopal, 1971), potato tubers (Rothe, 1974), cucumber seedlings (Bower et al., 1978), and pea seedlings (Miyata et al., 1981). Much attention has been focused on this enzyme because of its possible involvement ...

Patients with disseminated superficial actinic porokeratosis (DSAP) and linear porokeratosis (LP) exhibit monoallelic germline mutations in genes encoding mevalonate pathway enzymes, such as MVD or MVK. Here, we showed that each skin lesion of DSAP exhibited an individual second hit genetic change in the wild-type allele of the corresponding gene specifically in the epidermis, indicating that a postnatal second hit triggering biallelic deficiency of the gene is required for porokeratosis to develop. Most skin lesions exhibited one of two principal second hits, either somatic homologous recombinations rendering the monoallelic mutation biallelic or C>T transition mutations in the wild-type allele. The second hits differed among DSAP lesions but were identical in those of congenital LP, suggesting that DSAP is attributable to sporadic postnatal second hits and congenital LP to a single second hit in the embryonic period. In the characteristic annular skin lesions of DSAP, the central epidermis featured mostly second hit keratinocytes, and that of the annular ring featured a mixture of such cells and naïve keratinocytes, implying that each lesion reflects the clonal expansion of single second hit keratinocytes. DSAP is therefore a benign intraepidermal neoplasia, which can be included in the genetic tumor disorders explicable by Knudson's two-hit hypothesis.

No abstract

with different water contents. Arrows show the glass transition.

The production of hook protein and flagellin in 29 Fla- mutants of Escherichia coli K-12 was determined by the complement fixation assay. Six mutants produced hook protein, and four of them also produced flagellin. A flaE mutation was introduced into these fla mutants carrying the hook structure. All of these mutants made polyhooks and were used as hosts for a newly isolated host-range mutant of chi phage that has a high affinity for the hook structure. All except one mutant produced significant amounts of progeny phages. A flaD flaE double mutant was that exception which did not yield significant amounts of progeny by the phage propagation method. All of the flaE double mutants produced comparable amounts of polyhooks, and no qualitative difference was detected between chi-sensitive and chi-insensitive mutants by the complement fixation assay. Accordingly, it was thought that the polyhook of the flaD flaE mutant had a mechanical defect for chi phage infection. This assumption was confirmed by tethered-cell experiments; the flaD flaE mutant did not rotate. These results are well explained by a proposed regulation pathway of flagellar genes. flaE mutants can express other genes which govern the final step of the flagellar morphogenesis, whereas flaD mutants cannot rotate, possibly because the mocha operon is not expressed. The results obtained in E. coli were also found to be applicable to Salmonella typhimurium.