Sesquiterpenoids of Riccardia and Pallavicinia species

Riccardia species (Metzgeriales) contain various types of sesquiterpenes. R. jackii produces ent-selinane-, ent-aromadendrane-and ent-bicyclogermacrane-type sesquiterpenes together with (R)-cuparene and α-barbatene. Aneura pinguis (= Riccardia pinguis) is chemically quite different from R. multifida and R. jackii. The former produces a large amount of pinguisone. R. multifida contains 6-(3-methyl-2-butenyl)-indole and (+)-β-elemene as the major components. Pallavicinia longispina (Dilaenaceae; Metzgeriales) produces mainly spathulenol. The chiral properties of the sesquiterpenes isolated from R. jackii are quite similar to those of red algae, Laurencia species.     

Bibenzyls from Radula tokiensis and R. Japonica

A new bibenzyl having a dihydrooxepin ring was isolated from the acetone extract of the liverwort Radula tokiensis, together with the previously known 5 bibenzyls and 3 sesquiterpenes, trans-β-farnesene, cuparene and (Jcuparenol. Two known bibenzyls were isolated from R. japonica. The bibenzyl derivatives are significant chemosystematic markers of the Radulaceae.     

Photoreaction of tyrosin-iodinated bacteriorhodopsin at low temperature

To elucidate the role of tyrosine residues in the shift of max and the light-driven proton pump of bacteriorhodopsin~ the photochemical reaction of tyrosine-iodinated bacteriorhodopsin (tyr-mod-bR) was investigated by low-temperature spectrophotometry. After 4–5 of 11 tyrosine residues of bacteriorhodopsin were iodinated, the meta-intermediate of tyr-mod-bR in 75% glycerol solution became so stable that its decay could be observed even at room temperature and i t was stable in the dark for several hours at –65°C.Four batho-intermediates were formed by irradiation with green light (500 nm) at –170°C. Like native bacteriorhodopsin, these batho-intermediates were photoreversible at –170°C. Four corresponding meta-intermediates were also formed by irradiation at –60°C. Using the difference spectra between meta-intermediates and tyr-mod-bR, the absorption spectra of four kinds of tyr-mod-bRs, batho-intermediates, and meta-intermediates were estimated. Each was at shorter wavelengths than that of its corresponding type in native bacteriorhodopsin. The results indicate that two or more tyrosine residues have some role in determining color in native bacteriorhodopsin.     

The control of phosphoprotein phosphatase by the second-site phosphorylation of a substrate. Studies with H2B histone as model substrate.

The phosphorylation of Ser-32, in addition to Ser-36 of H2B histone, stimulated the rate of Pi release from Ser-36 by the small form (Mr 31 000) of pig heart phosphoprotein phosphatase both in the absence and presence of 50 mM magnesium acetate. By phosphorylation at Ser-32, the Km value for Ser-36 phosphate in H2B histone was increased from 0.38 microM to 1.16 microM in the absence of magnesium acetate, but not significantly changed (from 37.4 microM to 26.2 microM) in the presence of magnesium acetate. With the large form (Mr 224000) of the phosphoprotein phosphatase, however, the phosphorylation at Ser-32 suppressed the rate of Pi release from Ser-36 both in the absence and presence of magnesium acetate. The Km value of the large form for Ser-36 phosphatase in H2B histone was nevertheless increased by phosphorylation at Ser-32, from 1.2 microM to 5.3 microM in the presence of magnesium acetate, but not changed (from 0.26 microM to 0.23 microM) in the absence of magnesium acetate.     

Comparison of two forms of pig heart phosphoprotein phosphatase.

A phosphoprotein phosphatase (phosphoprotein phosphohydrolase, EC 3.1.3.16) was partially purified from pig heart using as substrate H2B histone which had been phosphorylated at Ser-32 and Ser-36 by adenosine 3',5'-monophosphate-dependent protein kinase (EC 2.7.1.37). The enzyme had a molecular weight of approx. 250 000 and was converted to a smaller form with a molecular weight of approx. 30 000 upon treatment with ethanol. Phosphorylase alpha (EC 2.4.1.1) and phosphorylated H1 histone also served as substrates for both forms of the enzyme. The conversion of the large form of the enzyme to the small form decreased the phosphohistone phosphatase activity to 25-50% with a concomitant 7-fold increase in the phosphorylase alpha phosphatase activity. Ser-36 phosphate was removed 6- and 15-fold more rapidly than was Ser-32 phosphate by the large and small forms of the enzyme, respectively. Among Ser-36-containing tryptic phosphopeptides derived from phosphorylated H2B histone, Lys-Glu-Ser(P)-Tyr-Ser-Val-Tyr was the shortest phosphopeptide which was dephosphorylated at a significant reaction rate with the phosphoprotein phosphatase. The Km values for phosphorylated H2B histone and the tryptic phosphopeptide were 23.7 micron and 187.1 micron, respectively, with the large form, and 81.4 micron and 90.0 micron, respectively, with the small form of the enzyme.     

Studies on the sites in histones phosphorylated by adenosine 3':5'-monophosphate-dependent and guanosine 3':5'-monophosphate-dependent protein kinases.

Adenosine 3':5'-monophosphate-dependent protein kinase (protein kinase A) purified from silkworm pupae phosphorylated five major fractions of calf thymus histone, whereas guanosine 3':5'-monophosphate-dependent protein kinase (protein kinase G) purified from the same organism reacted preferentially with H1, H2A, and H2B histones. Amino acid analysis of the phosphopeptides which were obtained by proteolytic digestion revealed that both protein kinases A and G showed the abilities to phosphorylate the same serine hydroxyl groups in H1 and H2B histones. Both protein kinases reacted with Ser-38 in H1 histone. With H2B histone as substrate protein kinase A phosphorylated Ser-32 as well as Ser-36, whereas protein kinase G reacted preferentially with Ser-32 and the reaction with Ser-36 was very slow. H3 and H4 histones were practically inactive substrates for protein kinase G. Although H2A histone has not been analyzed, the evidence has raised a possibility that protein kinase G utilizes a portion of the substrate proteins for protein kinase A.     

Effect of DL-alpha-hydrazino-delta-aminovaleric acid, an inhibitor of ornithine decarboxylase, on polyamine metabolism in isoproterenol-stimulated mouse parotid glands.

The effects of DL-alpha-hydrazino-delta-aminovaleric acid (DL-HAVA) on polyamine metabolism in isoproterenol(IPR)-stimulated mouse parotid glands were investigated both in vitro and in vivo. Using partially enzyme preparations, it was found that DL-HAVA strongly inhibited ornithine decarboxylase (EC 4.1.1.17) by competing with L-ornithine. Other enzymes metabolizing ornithine and pyridoxal phosphate-dependent enzymes were at least 2-3 orders of magnitude less sensitive to DL-HAVA than ornithine decarboxylase. Administration of DL-HAVA greatly depressed the increases in both the putrescine level and putrescine formation from L-ornithine induced by IPR in the mouse parotid glands. Under the same conditions, the stimulation of DNA synthesis and subsequent cell proliferation in the glands were also suppressed. However, the IPR-dependent increases in S-adenosyl-L-methionine decarboxylase (EC 4.1.1.50) activity, synthesis and the tissue concentration of spermidine, and RNA synthesis in the parotid glands were not affected appreciably by DL-HAVA. The inhibition of DNA synthesis by DL-HAVA was effectively prevented by putrescine, but not by spermidine or 1,7-diaminoheptane, given at the same time when DL-HAVA inhibited stimulation of putrescine formation by IPR. From these results, it is proposed that putrescine is involved in cell proliferation besides being a precursor of spermidine. The effects of methylglyoxal bis(guanylhydrazone) (MGBG), an inhibitor of S-adenosyl-L-methionine decarboxylase, on the metabolism of polyamines and nucleic acids in growing parotid glands were also examined.     

Effect of sodium dodecyl fulfate on the dissociation of bovine liver catalase.

Native bovine liver catalase [EC 1.11.1.6] and catalase acetylated with N-acetylimidazole (AI) both combined with sodium dodecyl sulfate (SDS) to form catalase-SDS complexes. The differences between native and acetylated catalase bound to SDS were investigated as regards enzymatic activity, absorption spectra, ORD and CD, sedimentation velocity and fluorescence spectra. It was found that the binding of SDS with both catalases depended on incubation time and SDS concentration, and that the acetylation of catalase had some protective effect on the denaturation of the molecule by SDS, which may be ascribed to a reduction of ionic interaction between SDS and the protein on acetylation. The native catalase was found to split into three smaller components on incubation with 1% SDS for 96 hr, whereas the acetylated catalase split into two smaller components. These smaller components were isolated by gel filtration through Sephadex G-100. The isolated components has estimated molecular weights of 60,000, 30,000, aide. It seemed likely that the modification occurred stepwise. Approximately 26% of the carboxyl groups of fibrinogen was modified finally. The modified fibrinogen had no interaction with cationic detergent, and did not form any complex with the detergent. In dilute acid, fibrinogen was observed to show only a slight interaction with cationic detergent. It is probable that the exposed and ionized carboxyl groups are essential for the formation of a complex between fibrinogen and cationic detergent.     

Two new iridoid glucosides from Ixora chinensis

From leaves and twigs of Ixora chinensis, two new iridoid glucosides, ixoroside (1) and ixoside (7,8-dehydroforsythide) (2) along with known geniposidic acid (3) have been isolated and their structures have been established.