Cloning of the gene coding for chitobiase ofSerratia marcescens

Summary A λ phage DNA library ofSerratia marcescens was constructed and a clone carrying the gene coding for chitobiase (E.C.3.2.1.29) was isolated and characterized. Deletion analysis limited the cloned region to 4.5 kb that is capable of efficient expression of chitobiase.Escherichia coli cells harboring a plasmid carrying the cloned gene express chitobiase constitutively. The molecular weight of the protein is about 95000 daltons. In exponentially growingE. coli cells the chitobiase enzyme was found to be secreted into the periplasm.     

Sequence of gonadal events and oestradiol levels in Sparus aurata (L.) under two photoperiod regimes

Individually tagged Sparus aurata were kept in tanks with running sea water (21°± 2°C) during their second and third years of life. Gonads were biopsied and blood was sampled at monthly intervals. Thirteen of 50 fish in the second year and 24 of 35 fish in the third year were phenotypically females. Fish kept under 16L/8D photoperiod from July 1981 to August 1982 did not reach maturation; waves of initial ovarian growth alternated with waves of atresia. When photoperiod was shortened as from August 1982, gonadal development commenced within a month and proceeded at a rate higher than that of the control fish reared under natural photoperiod. Under natural photoperiod oestradiol serum levels (E₂) were relatively low during the resting phase, May-October (108 ± 11 pg ml⁻¹), and during the late vitellogenic phase (502 ± 76 pg ml⁻¹). High levels (1669 ± 312 and 1240 ± 172pg ml⁻¹) occurred during the early vitellogenic and the maturational phases. The high level of E₂ during the spawning season of S. aurata is explained by earlier reports indicating a prolonged breeding season with daily release of eggs, and alternating daily surges of E₂ and 17α, 20β, dihydroxy-4-pregnen-3-one, possibly a 'maturational progestin' in this fish. In phenotypic males, E₂ was highest during early spermatogenic phases (745 ± 142pg ml⁻¹) but was low (155 ± 11 pg ml⁻¹) in males with running sperm.     

Novel Biotransformations of 7-Ethoxycoumarin by Streptomyces griseus

Biotransformation of 7-ethoxycoumarin by Streptomyces griseus resulted in the accumulation of two metabolites which were isolated and identified as 7-hydroxycoumarin and 7-hydroxy-6-methoxycoumarin. A novel series of biotransformation reactions is implicated in the conversion of the ethoxycoumarin substrate to these products, including O-deethylation, 6-hydroxylation to form a 6,7-dihydroxycoumarin catechol, and subsequent O-methylation. Either 7-hydroxycoumarin or 6,7-dihydroxycoumarin was biotransformed to 7-hydroxy-6-methoxycoumarin by S. griseus. Trace amounts of the isomeric 6-hydroxy-7-methoxycoumarin were detected when 6,7-dihydroxycoumarin was used as the substrate. Efforts to obtain a cell-free catechol-O-methyltransferase enzyme system from S. griseus were unsuccessful. However, [methyl-¹⁴C]methionine was used with cultures of S. griseus to form 7-hydroxy-6-[¹⁴C]methoxycoumarin.     

Involvement of an Inducible Cytochrome P-450 in Precocene II Oxidation by Streptomyces Griseus

Streptomyces griseus oxidizes the insecticide precocene II to its cis- and trans-dihydrodiols and 3-chromenol after growth on an enriched medium containing soybean flour. Oxidation of precocene II is dependent on the level of cytochrome P-450 in this organism. Extracts of cells grown on media lacking soybean flour were devoid of cytochrome P-450 and could not oxidize precocene II. In an in vitro reconstituted system containing NADPH, spinach ferredoxin reductase, spinach ferredoxin and ammonium sulfate fractions enriched in cytochrome P-450, precocene II was oxidized to its dihydrodiols. An aerial mycelium-negative variant of S. griseus (AMY mutant), that was unable to elicit cytochrome P-450 when grown on soybean flour-enriched medium, failed to oxidize precocene II.     

A unique genomic sequence in the Wolf-Hirschhorn syndrome [WHS] region of humans is conserved in the great apes

The Wolf-Hirschhorn syndrome (WHS) is caused by a partial deletion in the short arm of chromosome 4 band 16.3 (4p16.3). A unique-sequence human DNA probe (39 kb) localized within this region has been used to search for sequence homology in the apes' equivalent chromosome 3 by FISH-technique. The WHS loci are conserved in higher primates at the expected position. Nevertheless, a control probe, which detects alphoid sequences of the pericentromeric region of humans, is diverged in chimpanzee, gorilla, and orangutan. The conservation of WHS loci and divergence of DNA alphoid sequences have further added to the controversy concerning human descent.     

BRCA1 maps proximal to D17S579 on chromosome 17q21 by genetic analysis

Previous studies have demonstrated linkage between early-onset breast cancer and ovarian cancer and genetic markers on chromosome 17q21. These markers define the location of a gene (BRCA1) which appears to be inherited as an autosomal dominant susceptibility allele. We analyzed five families with multiple affected individuals for evidence of linkage to the BRCA1 region. Two of the five families appear to be linked to BRCA1. One apparently linked family contains critical recombinants, suggesting that the gene is proximal to the marker D17S579 (Mfd188). These findings are consistent with the maximum-likelihood position estimated by the Breast Cancer Linkage Consortium and with recombination events detected in other linked families. Linkage analysis was greatly aided by PCR-based analysis of paraffin-embedded normal breast tissue from deceased family members, demonstrating the feasibility and importance of this approach. One of the two families with evidence of linkage between breast cancer and genetic markers flanking BRCA1 represents the first such family of African-American descent to be reported in detail.     

Biocatalysis in natural products chemistry

The properties of enzymes and microbial cells as biocatalysts useful in natural products chemistry are discussed from the perspective of the chemical transformations they catalyse. Attention is focused on numerous reactions of value to natural products chemists, including the acyloin condensation, Baeyer-Villiger oxidation, regio- and enantioselective ester hydrolyses, oxidations of aromatic and non-aromatic substrates, oxidoreduction and O- and N-dealkylations. Compounds considered in this review include amino acids, alkaloids, antibiotics, coumarins, naphthoquinones, quassinoids, rotenoids and mono-, sesqui-, di- and triterpenoid substrates. The value of biocatalysis compared with traditional chemical catalysis is considered within the broad framework of natural products chemistry, and the potential for using immobilized enzyme and cell technology is presented.