Cell-free extracts capable of converting 14C1-labeled gibberellins (GAs) were prepared from spinach (Spinacia oleracea L.) leaves. [i4C1-labeled GAs, prepared enzymically from I'4Clmevalonic acid, were incubated with these extracts, and products were identified by gas chromatography-mass spectrometry. The following pathway was found to operate in extracts from spinach leaves grown under long day (LD) conditions:GA,2-+ GA53-+ GA44--GA,9 --GA20. The pH optima for the enzymic conversions of I'4CiGAs3 I`4CIGA44 and I`4CIGA,, were approximately 7.0, 8.0, and 6.5, respectively. These three enzyme activities required Fe2, a-ketoglutarate and 02 for activity, and ascorbate stimulated the conversion of I'4CIGAs3 and I'4C]GA19. Extracts from plants given LD or short days (SD) were examined, and enzymic activities were measured as a function of exposure to LD, as well as to darkness following 8 LD.The results indicate that the activities of the enzymes oxidizing GA53 and GA,9 are increased in LD and decreased in SD or darkness, but that the enzyme activity oxidizing GA," remains high irrespective of light or dark treatment. This photoperiodic control of enzyme activity is not due to the presence of an inhibitor in plants grown in SD. These observations offer an explanation for the higher GA20 content of spinach plants in LD than in SD.Spinach (Spinacia oleracea L.) is a LD rosette plant in which stem growth in LD is mediated by GAs2 (19,20). Six 13-hydroxylated GAs have been identified in spinach leaves (14). Of these, GA53, GA44, GA,9, GA20, and GA29 are related metabolically as shown in Figure 1. Although all the steps of this pathway have not been unequivocally demonstrated in spinach, the evidence strongly suggests that the pathway does operate (5,16).When spinach plants grown in SD are transferred to LD the level of endogenous GA,9 decreases, while levels of GA20 and GA29 increase ( 15). This suggests that the photoperiod regulates the conversion of GA,9 to GA20, which is essential for stem growth. Further evidence for this hypothesis was put forward by Gianfagna et al. (5) GA metabolic pathways have been extensively studied using

The chemical structure of the new angucycline antibiotic landomycin A has been elucidated via chemical and spectroscopic methods, in particular by 2D NMRcorrelation spectroscopy, e.g., 1H,1H-COSY, 13C,1H-COSY, correlation spectroscopy via long-range-couplings and heteronuclear multiple bond connectivity spectroscopy sequences. The spectroscopic investigations were carried out principally with the octaacetyl derivative of landomycin A, which is more soluble in organic solvents than landomycin A itself. The structure consists of a new, unusual angucyclinone, landomycinone A, and of six deoxy sugars, four D-olivoses and two L-rhodinoses, which are all assembled in one chain thus forming the sequence (olivose-4-* l-olivose-3 -» l-rhodinose)2. This long sugar chain is bondedas a phenolic glycoside to the aglycone moiety, a unique structural feature amongquinone glycoside antibiotics. By comparison with the main component landomycin A, the structures of three minor congeners, namely landomycins B, C and D, could be proposed.Angucycline antibiotics1* are a growing group of antibiotic glycosides with interesting and diverse biological activities including antibacterial, enzyme inhibitory and cytostatic effects. Recent examples of this group of antibiotics also show activity as platelet aggregation inhibitors2'3).In our screening program for antitumor compoundswe found an orange solid as the major bioactive metabolite of Streptomyces sp. (DSM5087). This compound was subsequently named landomycin A. While the fermentation and biological properties of the strain DSM5087 as well as the isolation of the crude product and the biological activities of the antibiotic compounds will be a subject of an additional paper4), we report here the physico-chemical characterization and the structure elucidation of the landomycins A~D. ResultsThe FAB-MS of landomycin A (1) gave both m/z 1,089 ((M+2H+H)+, positive ions) and m/z 1 ,087 ((M + 2H -H)" , negative ions). Using the FABmethod, quinone antibiotics commonly give molecular

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A cell-free system prepared from developing seed of runner bean (Phaseolus coccineus L.) converted [(14)C]gibberellin A12-aldehyde to several products. Thirteen of these were identified by capillary gas chromatography-mass spectrometry as gibberellin A1 (GA1), GA4, GA5, GA6, GA15, GA17, GA19, GA20, GA24, GA37, GA38, GA44 and GA53-aldehyde, all giving mass spectra with (14)C-isotope peaks. GA8 and GA28 were also identified but contained no (14)C. All the [(14)C]GA12-aldehyde metabolites, except GA15, GA24 and GA53-aldehyde, are known endogenous GAs of P. coccineus.

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