Aldolase--An Important Enzyme in Controlling the Ribulose 1,5-bisphosphate Regeneration Rate in Photosynthesis

This study was done to explore an enzymatic mechanism for thephotosynthetic carbon reduction cycle whereby the rate of synthesisof ribulose 1,5-bisphosphate (RuBP) could be changed while thelevels of intermediates other than 3-phosphoglycerate and RuBPwere kept constant. Chloroplast aldolase was purified to homogeneityfrom spinach leaves. When the enzyme was assayed in the directionof fructose 1,6-bisphosphate synthesis in the presence of theconcentrations of the substrates reported in vivo, the activitywas severely inhibited by physiological concentrations of RuBP.The aldolase reaction proceeded with a sequential mechanism.The K_m for dihydroxyacetone phosphate and D-glyceraldehyde 3-phosphatewere 0.45 mM and 40 µM, respectively. The activity wascompetitively inhibited by RuBP with respect to dihydroxyacetonephosphate. The K^I was 0.78 mM. The maximum activity of aldolasein spinach leaves was calculated as 1,360µmol (mg Chl)^–1h^–1 An equation to express the reaction for the synthesisof fructose 1,6-bisphosphate by aldolase was constructed topredict the metabolic rate of this reaction in vivo. The calculationclearly showed that aldolase is an important enzyme in controllingthe rate of RuBP regeneration. (Received March 25, 1991; Accepted August 12, 1991)     

TWO MORPHOLOGICALLY SIMILAR BIOLOGICAL SPECIES: CHONDRUS PINNULATUS AND C. ARMATUS (GIGARTINACEAE,RHODOPHYTA)1

The nature of the relationship between Chondrus pinnulatus (Harvey) Okamura f. pinnulatus and C. pinnulatus f. armatus (Harvey) Yamada et Mikami (Gigartinaceae, Rhodophyta) was investigated by comparative analysis of their biogeography, phenologies, life histories, gross and vegetative morphology, crossability, and upper thermal tolerance. The forma pinnulatus has a more northerly distribution in Japan and adjacent waters, exhibiting adaptation to the cooler regions, whereas the forma armatus has a more southerly range. The latter may be the result of a higher thermal tolerance. Both formae have a Polysiphonia-type life history and are similar in their internal vegetative morphology. They can, however, be distinguished by gross morphology: forma pinnulatus has wide, flattened axes, compressed to flattened ultimate segments and proliferations, while forma armatus has narrow, compressed to subterete axes and subterete to terete ultimate segments and proliferations. These differences persist in laboratory culture. All intraformae crosses were positive, with carpospores from the cross developing into fertile F₁ tetrasporophytes releasing tetraspores that developed into dioecious F₁ gametophytes, the female gametophytes of which formed normal cystocarps. This suggests that members of populations of each forma freely interbreed. Among interformae crosses, only some offspring derived from geographically distant strains bore normal cystocarps in the F₁ female gametophytes. Other crosses showed that interbreeding between populations of these two formae was blocked by various isolating mechanisms: incompatibility, hybrid inviability, and hybrid sterility. Reproductive isolation between f. pinnulatus and f. armatus is virtually complete in wild populations, because hybrid populations have not been found in the wild. In addition, these two entities can be considered biological species that are also referred to the taxonomic species, C. armatus and C. pinnulatus, because they do not overlap with regard to the morphology of the ultimate segments and proliferations. Subtle (but significant) gross morphological differences, partial interfertility between the two species, and deleterious hybridization in the area in which they occur sympatrically suggest that their evolutionary divergence was relatively recent.     

A Comparative Study of Mycobacteria from Patients' Room Dusts and from Sputa of Tuberculous Patients

The source of mycobacteria other than Mycobacterium tuberculosis occurring in sputa of tuberculous patients as casual isolates was investigated by comparing the occurrence rate of mycobacterial species between patient's room dust and patient's sputum. Almost all species of mycobacteria recovered from sputa could be found in dusts obtained from the rooms. However, the percentage of occurrence of the mycobacterial species in dusts differed from that in sputa. In dusts, Mycobacterium fortuitum (39.6%), Mycobacterium nonchromogenicum (23.5%) and Mycobacterium gordonae (16.7%) occurred in high frequencies, whereas Mycobacterium intracellulare (69.6%), M. gordonae (5.9%), Mycobacterium scrofulaceum (5.2%), and Gordona bronchialis (10.4%) were the main species found in sputa. The patterns of occurrence of mycobacterial species as illustrated above may suggest that pathogenic mycobacteria survive in the respiratory tract while nonpathogenic ones are destroyed there, thus the human body acts as a selective medium for the pathogenic mycobacterial species. Serotype studies on strains of M. intracellular as casual isolates indicated that those from sputa of tuberculous patients were different from those derived from patients with lung diseases due to this species of mycobacteria. These results led us to the conclusion that mycobacteria in patients' room dusts were the source of mycobacteria occurring in sputa as casual isolates, particularly the pathogenic mycobacteria in dusts are more likely to survive in the human respiratory tract, occasionally multiplying and causing disease under favorable circumstances.     

A Further Numerical Taxonomic Study of the Rhodochrous Group

A computer taxonomy was carried out as an aid to clarify the relationships between the genera Mycobacterium, and Nocardia as well as the ‘Rhodochrous’ group. The last group contained slightly acid-fast organisms isolated from sputa and soil and also included strains received as “Mycobacterium rhodochrous.” The group had been proposed as the genus Gordona by the present author. The rhodochrous group formed a cluster at the 87% similarity level and was clearly separated from all strains of the genera Mycobacterium and Nocardia. The cluster of the rhodochrous group was divided into seven subclusters at the 90% similarity level, and six of the seven corresponded to six species of the genus Gordona: G. bronchialis; G. rubropertincta (synonym G. rubra); G. terrae; G. aurantiaca; G. rhodochroa; G. rosea. If one accepts the concept that a phenetically well-defined cluster is a species, each of the subclusters of the rhodochrous group should be regarded as a species and the entire group as a genus. Discrepancies between the results of numerical classification and the results of lipid analyses remain as a problem to be solved in the future.     

Synthesis of a New Series of Z-Amino Acid and Z-Dipeptide Chloromethyl Ketone Derivatives

The synthesis of a new series of N^α-benzyloxycarbonyl (Z)-amino acid and Z-dipeptide chloromethyl ketone derivatives is described. The new derivatives are as follows; Z-l-Leu-CH₂Cl, Z-l-Phe (N0₂)-CH₂Cl, Z-l-Tyr (Bzl)-CH₂Cl, Z-l-Tyr (Z)-CH₂Cl, Z-l-Tyr-CH₂Cl, Z-l-Glu (Me)-CH₂Cl, Z-l-Phe-l-Leu-CH₂Cl, Z-l-Tyr-l-Leu-CH₃Cl, Z-l-Leu-l-Phe-CH₂Cl, Z-l-Leu-l-Tyr-CH₂Cl, Z-l-G1U (Me)-l-Tyr-CH₂Cl, Z-l-G1U (Me)-l-Phe-CH₂Cl.     

Regulation of l-Glutamate Biosynthesis by Copper Ions

A specific regulatory effect of copper ions on the microbiological synthesis of l-glutamate from acetate was found. The minimal concentration of copper ions necessary for the maximal production of l-glutamate was about 0.025 µg/ml at which the yield of l-glutamate was four times greater than that in the absence of copper ions. This effect of copper was demonstrated only when acetate was the substrate; it was not observed when the substrate was glucose ethanol, lactate or n-paraffin.

The physiological features of the l-glutamate production from acetate were examined in the presence or absence of copper ions. The most striking features of the culture without added copper ions were the increase in Q_O2 and NADH oxidase and the marked reduction of succinate oxidase accompanied with the reduction of l-glutamate formation. In addition, the regulation of l-glutamate synthesis by copper ions proved to have no relation to the wellknown regulatory factor, cell permeability. These facts suggest that the l-glutamate biosynthesis from acetate is regulated through unknown factors related to the respiratory activities.     

A Rapid Isolation of the Unknown 5′-Flanking Sequence of Human CENP-B cDNA with Polymerase Chain Reactions

We rapidly and efficiently isolated the 5′-region of cDNA encoding the N-terminal region of human centromere antigen B (CENP-B) including an ATG methionine codon by polymerase chain reactions (PCR). The unknown 5′-flanking sequence of the cDNA was amplified using an adaptor-sequence ligated to the 5′ end as a universal primer sequence. To locate the target fragments, we did an additional PCR with another set of two internal primers using samples of the size-fractionated products as templates, rather than using the conventional hybridization procedure. This approach can further be applied to the analysis of other unknown flanking sequences of cDNA or genomic DNA.     

In Vitro Peptidoglycan Synthesis Which is Very Sensitive to Cephalexin and Penicillin G in Escherichia coli: Presumable Septum-forming Reaction Sequence

Hydrangeae Dulcis Folium, the fermented and dried leaves of Hydrangea macrophylla SER. var. thunbergii MAKINO, suppressed D-galactosamine-induced liver injury by 85.2% when added to the diet at 1% and fed to rats for fifteen days. The hepatoprotective effect is more potent than that of a milk thistle extract and turmeric powder. Some fractionated extracts showed hepatoprotective activity in the D-galactosamine-induced in vitro liver injury model.     

Mode of Action of a New Aspergillus oryzae Carboxypeptidase O-1

DNA breakage by hydrolyzable tannins of known structures was investigated by agarose or polyacrylamide gel electrophoretic analysis. Hydrolyzable tannins could cause both double-strand and single-strand breakages in λDNA in the presence of Cu²⁺. The breaking reaction was strongly suppressed at concentrations higher than 100 μm of hydrolyzable tannins. DNA breakage by various tannins was dependent upon their sorts, numbers, and binding sites of the constituent acids and polyalcohols. Metallic ions other than Cu²⁺ had little effect on the breaking reaction.