RNA metabolism in the venom glands of Vipera palaestinae was studied at different stages after manual extraction of the venom (milking). The rate of (32)P incorporation into gland RNA was found to be maximal at 1-4 days after milking in correlation with the height of the secretory epithelium. Venom production attained a maximum only after 8-16 days, in parallel with the accumulation of stable species of cellular RNA.

Using manometric and enzymic techniques, H2 and CO2 evolution in darkness and light has been studied in the green alga Chianydomonas reinhardtii F-60. F-60 is a mutant strain characterized by an incomplete photosynthetic carbon reduction cycle but an intact electron transport chain.In the dark, starch was broken down, and H2 and CO2 was released. The uncoupler, carbonyl cyanide m-fluorophenylhydrazone with an optimum concentration of 5 to 10 micromolar, increased the rate of CO2 release and starch breakdown but depressed H2 formation. It m-fluorophenylhydrazone, stimulated H2 photoproduction by removing ATP which limited the sequence of reactions. The contribution of photosystem II to the photoproduction of H2, as judged from the effect of 10 micromolar 3-(3,4-dichlorophenyl)-1,1-dimethylurea, was at least 80%.CO2 photoevolution increased Unearly with time, but H2 photoevolution occurred in two phases: a rapid initial phase folowed by a second slower phase. The rate of H2 release increased hyperbolically with light intensity, but the rate of CO2 production tended to level off and decrease with increasing light intensity, up to 145 watts per square meter. It was proposed that a changing CO2 and H2 ratio is the result of interaction between the carbon and hydrogen metabolism and the photosynthetic electron transport chain.Studies with chlorophyllous algae have established that H2 evolution in the light is the result of electron transport through the photosystems associated with an adaptable hydrogenase. These algae also produce H2 in the dark but at a lower rate. Two mechanisms have been proposed to account for H2 release in the light, while the pathway for the dark release of H2 has received 'Supported by Department of Energy (10-EY-76-5-02-3231) and National Science Foundation (PCM 79-22612 light (3, 14). It is known that gas evolution is stimulated by added glucose (5). Data obtained with position-labeled glucose led Kaltwasser et al. (13) to propose that classical glycolysis in Scenedesmus obliquus is the pathway involved. From a stoichiometric analysis of the products-which included ethanol, glycerol, and acetate, in addition to CO2 and H2-Klein and Betz (15) also proposed glycolysis for the heterofermentative breakdown of the reserve substance, starch, in Chlamydomonas reinhardii. This suggestion was supported by a similar fermentation pattern in Chlorella vulgaris (22). On the basis of a depression of H2 evolution in the dark by uncouplers of phosphorylation, Gaffron and Rubin (5) suggested that the fermentation yielded not only CO2 but also ATP. ATP would be required to raise the redox potential of the electrons from the reductant (NADH) to a higher one necessary for H2 production. In contrast to inhibiting H2 evolution in the dark, the uncoupler elevated the photorelease of H2 and CO2. Acetate has been reported to stimulate H2 evolution insensitive to DCMU, and Healy (10) suggested an anaerobically functioning citric acid cycle in Chlamydomonas moewusii to explain this observation. In his formu...

Several workers (2,3,4,5,10)

A 2-fold increase in the rate of CO., fixation following the addition of fructose-1,6-diP. ribose-5-P, glucose-1-P, glucose-6-P, fructose-6-P or glyceric acid-3-P to a fragmented spinach chloroplast system was demonstrated by Arnon et al. (1) and Whatley et al. (22). However, there are no reports on the effect of these compounds on the rate of CO., fixation by intact spinach chloroplasts. It became important to extend the work of Arnon.Whatley. and Allen to the intact chloroplast using these and other phosphorylated substances after the demonstration by Havir and Gibbs (14) that the intact chloroplast in sharp contrast to the broken chloroplast preparation possesses the complete reductive pentose-P cycle. In the present work, we report on the varying effects of a number of phosphorylated compounds, principally phosphorylated sugars, upon the uptake of CO., fixation by intact spinach chloroplasts.5 We also report the effects of some of these compounds on CO. fixation in the presence of arsenite and iodoacetamide, 2 substances which inhibit the carbon cycle but appear to have little influence upon the photochemical act (8,11 In experiments where compounds were isolated for isotopic distribution, the system was similar to that described for CO., uptake with the following exceptions: 10 ml of reaction mixture were incubated in 150 ml Warburg vessels and the specific activity of the NaHC140. was increased such that 1 ml of reaction mixture contained 2 moless of NaHCO2 with 50 'Uc of C14. The reaction was stopped by boiling the contents of the flasks for 2 minutes. After centrifugation. an aliquot of the supernatant solution was assayed for isotopic content. Components of the mixture were separated by gradient elution with HCl from a Dowex 1-chloride column (14). Other procedures used were similar to those described in a previous publication (14).Reagents. D-Fructose-1 ,6-diP, D-glucose-6-P. Dribose-5-P, and L-a-glycerol-P were purchased from the Sigma Chemical Company. D-Fructose-6-P was obtained from C. F. Boehringer. D-Erythrose-4-P. D-glyceraldehyde-3-P, dihydroxyacetone-P, glycola.l]dehyde-P, and P-enolpyruvate were purchased from Calbiochem. D-Sedoheptulose-7-P and D-sedoheptulose-1 .7-diP were gifts from B. L. Horecker.

The relation between the rate of electron transport, ApH, and internal pH was studied in lettuce chloroplasts, by following, in parallel, the fluorescence quenching of 9-aminoacridine and the rate of electron transport. At low external pH (< 8.0) there was an initial burst in the rate of electron transport (R,) followed by a slower steady-state rate (R2). However, at high external pH (> 8.5) R, was slower than R,. Nevertheless, when analyzed as a function of internal pH, both R, and R, showed the same dependence with a maximal rate observed around internal pH 5.0. Thus, a t low external pH, the initial pH is initially around 5.0 and, therefore, R, is high, but as ApH is increased, the internal pH falls below 5.0 and R, is lower. At high external pH, the internal pH is initially above 5.0 and, therefore, R, is relatively low. As ApH increases the internal pH is lowered toward 5.0 and R, becomes faster. A similar conversion of the ratio RJR, from RJR, > 1 to RJR, < I was also observed a t constant external pH by varying the light intensity, or concentration of the uncoupler nigericin.In the presence of nigericin or a t low light intensities, the maximal rate was shifted to higher internal pH values. At internal pH values above 5.0 in the presence of nigericin, the rate of electron transport was inversely proportional to ApH. These results indicate that the internal pH is not the only parameter that controls the rate of electron transport. It is shown that when all these diverse results are plotted as a function of an average pH (between the internal and external pH) they show a single optimum. Thus, it is suggested that the rate controlling site is embedded in the thylakoid membrane, and is a function of both the internal and external pH. This membrane pH and the size of ApH seem to be the major factors controlling the rate of electron transport in chloroplasts.The kinetics of electron transport in chloroplasts was shown to depend strongly on the external pH (pH,) and also to be very sensitive to the energetic state of the chloroplast [1,2]. It is now recognized that a major component of the energetic potential in chloroplasts can be expressed in the form of a proton concentration gradient (ApH) [3]. We have recently developed methods for the determination of ApH in chloroplasts [4-61 which enable us to examine the relation between internal pH, ApH and the kinetics of electron transport. We have previously suggested that in addition to the control of the rate of electron transport by ApH, there is a strong dependence of the rate of electron transport on the internal pH @Hi) with a sharp maximum between pHi 5 and 6 [4]. This suggestion provides a reasonable explanation for the shift of the maximum rate of electron transport toward a more acidic pH which Abbreviation and Symbols. Tricine, N-trisjhydroxy methy1)methylglycine; pH,, medium pH; pH,, pH of inner thylakoid space; R,, initial rate of electron transport; R,, steady-state rate of electron transport.is observed in the presence of uncouplers [1,2]. The inhibit...