The Development of Activities of Some Enzymes Concerned with Glycollate Metabolism in Greening Bean Leaves

The activities of phosphoglycollate phosphatase (EC 3.1.3.18 [EC] ),glycollate oxidase (EC 1.1.3.1 [EC] .). catalase (EC 1.11.1.6 [EC] ), theperoxisomal NADH-glyoxylate reductase (EC 1.1.1.26 [EC] ) which isconsidered to function as a hydroxypyruvate reductase in theperoxisomes, and the chloro-plastic NADPH-dependent glyoxylatereductaae, have been measured in extracts prepared from 14-d-olddark-grown bean leaves during the course of their greening inresponse to exposure to continuous illumination. All of theenzymes were found in the dark-grown leaves and on a per-leafbasis the activities increased from 6- to 12-fold with the exceptionof a 2–3-fold increase of NADPH-dependent glyoxylate reductaseduring 96-h greening, while the activities either remained constantor declined during similar periods in darkness. Initial lagperiods were evident before the illumination-induced increasesin enzyme activities. As D-threo-chloramphenicol did not affectthe increase in activity of any of these enzymes it would appearthat the increases were in no way dependent on protein synthesisby 70S ribosomes, or on the development of photosynthetic activity.     

Biosynthesis of Deoxyribonucleotides in Ochromonas malhamensis

SYNOPSIS. Uniformly ¹⁴C-labeled pyrimidine ribonucleosides and orotic-6-¹⁴C acid were fed to growing cultures of Ochromonas malhamensis and the radioactivity appearing in RNA and DNA was determined. The carbon skeletons of uridine and cytidine were incorporated intact into all of the pyrimidine nucleotides from RNA and DNA. Incorporation of radioactivity into the purine nucleotides was negligible. The evidence supports the conclusion that deoxyribonucleotide biosynthesis in this organism proceeds via a pathway involving the direct reduction of the corresponding ribonucleosides or ribonucleotides. An important role for a trans-N-deoxyribosylase in deoxyribonucleotide biosynthesis here appears to be ruled out.     

Plastid Development in Primary Leaves of Phaseolus vulgaris: FREE NUCLEOTIDE CONCENTRATIONS IN GREENING LEAVES

The free nucleotides of 14-day-old dark-grown bean leaves havebeen extracted by perchloric acid and fractionated by ion-exchangechromatography. AMP, ATP, CMP, GMP, GDP, ADP-ribosephosphate(the acid-breakdown product of NADPH), NADP⁺, UMP, UDP-glucose,and UDP-xylose were the main components identified. During 45h continuous illumination greening occured and there was a 192per cent increase in the total free nucleotide per leaf. Mostof the constituent nucleotides showed rises during greening,the most notable increases being of substances concerned withphotosynthesis, namely NADPH, and UDP-glucose. A rise in theNADPH/NADP⁺ ratio after 15 h illumination appeared to signifythe onset of photosynthesis.     

Plastid Development in Primary Leaves of Phaseolus vulgaris: THE EFFECT OF SHORT BLUE, RED, FAR-RED, AND WHITE LIGHT TREATMENTS ON DARK-GROWN PLANTS

An investigation has been made on the effects of short exposuresto low intensities of blue; red, far-red, and white light, seperatelyand in certain combinations, on primary leaf growth and on theactivities of some chloroplastic and cytoplasmic enzymes ofdark-grown beans. Three distinct types of promotive responsehave been reccognized. (i) one dependent on the formation ofphytochrome-730 (p730). (ii) another dependent on one (protochlorophyll)or more non-phytochrome red-absorbing susbstances, and (iii)a positive interaction of successive treatment with red andblue light. Only the photocon version of protochlorophyll appearsto be a photoresponse specific to the plastids. As the otherresponses show effects of equal magnitude on both chloroplasticand cytoplasmic components and as P730 induces considerableleaf growth the sites of the primary responses are probablynot located in the plastids.