ISSN:0006-3592    

DOI:10.1002/bit.260100302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractConditions for the efficient conversion of commercial RNA to nucleoside 5′‐monophosphate by means of a phosphodiesterase in malt sprouts have been determined. A comparison of the enzyme content of the rootlets, stems, and kernels of various plant seedlings, including barley, rye, oat, wheat, rice, and beans shows maximum amounts in the rootlets, and minimum quantities in the ungerminated kernels. Of all the seedlings tested, (mung bean, soy bean, oat, wheat, rice, barley) barley gave the highest conversion of RNA to 5′‐nucleotides. Commercial malt sprouts prepared from 6 different malted barleys including 2‐rowed and 6‐rowed samples all showed about the same amount of phosphodiesterase content. Besides phosphodiesterase, other enzymes capable of hydrolyzing RNA and 5′‐nucleotides were found in sprouts. These included 3′‐phosphodiesterases, 5′‐nucleotidases, and nucleosidases. By carefully pretreating both extracts and the solid sprouts at elevated temperatures for a limited time and by the addition of minimum amounts of Zn+2, the action of these undesirable enzymes was either effectively destroyed or minimized so that the production of 5′‐nucleotides was maximized. It was found that suspensions of appropriately washed and treated barley malt rootlets are substantially more effective than aqueous extracts for conve

ISSN:0006-3592    

DOI:10.1002/bit.260100303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractMicrococcus sodonensisKY 3765 andArthrobacter citreusKY 3155 were found capable of accumulating IMP in media supplemented with hypoxanthine as a precursor. High concentrations of phosphate and magnesium salts were required for high yields of IMP. Manganese deficiency in the media was also essential. Excessive Mn2+effects were also seen in the IMP fermentation carried out with an adenineless mutant, ofCornynebacterium glutamicum. InM. sodonensis, R5P‐like substances, 5‐phosphoribose pyrophosphokinase and IMP pyrophosphorylase, were leaked out, of the cells grown in suboptimal Mn2+levels. This excretion was inhibited by high levels of Mn2+. Such a phenomenon was not noted inA. citreus.An adenineless mutant (KY 7208) ofBrevibacterium ammoniageneswas found to accumulate an appreciable amount of IMP. The chemical changes in this fermentation showed that, hypoxanthine was first producedde novo, excreted, and then reconverted into IMP by asalvagepathway. When hypoxanthine was added to 7208 culture, IMP yield was increased appreciably. In fact exogenous14C‐hypoxanthine was incorporated into14C‐IMP. Subsequent experiments showed that indeedBr. ammoniagenesATCC 6872, a parent culture of KY 7208, was able to produce IMP, GMP, and AMP, in good yield from hypoxanthine, guanine, and adenine, respe

ISSN:0006-3592    

DOI:10.1002/bit.260100304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractA major problem involved in the direct fermentation of nucleotides is their breakdown by phosphohydrolases. Thus, adenine auxotrophs of most microorganisms produce hypoxanthine and/or inosine rather than inosine 5′‐monophosphate (IMP) while guanine auxotrophs excrete xanthosine rather than xanthosine 5′‐monophosphate (XMP). Examination of aBacillus subtilismutant producing hypoxanthine plus inosine revealed at least four phosphohydrolases, three of which could attack nucleotides. Even when the extracellular nucleotide phosphohydrolase was inhibited by Cu+2and its surface‐bound alkaline phosphohydrolase was repressed and inhibited by inorganic phosphate, or removed by mutation, the breakdown products were still the only products of fermentation. Under these conditions, the third enzyme, a surface‐bound non‐repressible nucleotide phosphohydrolase was still active. It appears, at least inB. subtilis, that excretion is dependent upon breakdown by this enzyme and if hydrolysis does not occur, excretion of purine nucleotides is feedback inhibited by the resultant high intracellular IMP concentration.Corynebacterium glutamicummutants, on the other hand, can excrete intact nucleotides, and direct fermentations for IMP, XMP, and GMP have been described. An examination of phosphohydrolases in a GMP‐producing culture revealed no extracellular or surface enzymes. Disruption of the cells resulted in liberation of cellular phosphohydrolase activity with a substrate specificity remarkably similar to the flavorenhancing properties of the 5′‐nucleotides. The order of decreasing susceptibility was GMP, IMP, XMP; A

ISSN:0006-3592    

DOI:10.1002/bit.260100305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractA novel and convenient method for the synthesis of guanosine is described. The reaction of AICA‐riboside with sodium methylxanthate gave 2‐mercaptoinosine in almost quantitative yield. The latter was oxidized with hydrogen peroxide to afford inosine‐2‐sulfonic acids, which was readily animated to give guanosine in excellent yield. Similarly, the preparation ofN2‐methylguanosine andN2,N2‐dimethylguanosine, minor constituents of transfer RNA, was also accomplished. Furthermore, this procedure was extended to the synthesis of 2′,3′‐O‐isopropylideneguanosine and the isopropylidene derivatives of variousN2‐substituted guanosines from 2′,3′‐O‐isopropylidene‐AICA‐riboside. Guanosine via 2′,3′‐O‐isopropylideneguanosine was successfull

ISSN:0006-3592    

DOI:10.1002/bit.260100306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractRat liver was subjected to three different, disruption procedures (homogenization, explosive decompression, and Chaikoff press) and mitochondria were subsequently isolated by conventional differential Centrifugation and by zonal Centrifugation. The properties of these mitochondria were investigated by polarographic measurement of oxygen uptake and they were examined by electron microscopy. All three methods of disruption gave mitochondria which showed respiratory control. Nitrogen cavitation gave the most reproducible conditions for cell breakage and zonal Centrifugation gave good separation of subcellular organdies in extracts produced by this method. Some separation of the heterogenous mitochondrial populations was achieved by zonal Centrifugation.

ISSN:0006-3592    

DOI:10.1002/bit.260100307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractThe mechanism of oxygen transfer through a pure culture floc ofZoogloea ramigeraI‐16M has been described quantitatively. Oxygen uptake rates for both blended and nonblended floc particles indicated that, at a certain dissolved oxygen concentration, diffusion of oxygen through the floc matrix was the mechanism controlling the rate of oxygen utilization by the floc. This mechanism was quantitatively described by determining the oxygen diffusivity values for the floc. The diffusional distances of the floc particles along with the oxygen utilization rates of the floc were measured on floc grown under various conditions. Anoxic core equations were then used to calculate the oxygen diffusivity values for each experiment. These diffusivity values were then used to estimate the oxygen concentrations necessary in activated sludge plant

ISSN:0006-3592    

DOI:10.1002/bit.260100308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractPolyribonucleotide: orthophosphate nucleotidyl transferase, commonly known as polynucleotide phosphorylase catalyzes the reversible polymerization of ribonucleoside diphosphates with the liberation of orthophosphate. The equilibrium constant is approximately 1.0. Although isolated from a variety of sources, the enzyme occurs essentially as two types: one which does not require a primer for reaction initiation and a second which does. A parallel study of anE. colipreparation representing the first type and anM. lysodeikticuspreparation representing the second showed differences other than the primer requirement. Rates of polymerization were different as were theKms. TheE. colipreparation catalyzed the synthesis of polyguanylic acid while theM. lysodeikticuspreparation did not although synthesis of hetoropolymers containing guanylic acid was catalyzed by theM. lysodeikticusenzyme. Use of repurified commercial substrates made the validity of some primer‐requirement experiments suspect. End group analysis of product polymers served only to raise questions concerning the reaction‐initiating compounds and the reaction mechanism. A study of hetero‐polymer synthesis showed not only that the rate of polymerization was different, from that of homopolymers but that uncompetitive inhibition rather than competitive inhibition occurred when two ribonucleoside diphosphates were present in the reaction mixture. Furthermore, the experiments showed a preferential uptake of one substrate over another and an “enrichment” which was constant. It has also been shown that RNA polymerase, a DNA‐RNA directed polymerase, can be used to synthesize polyribonucleotides if the appropriate template

ISSN:0006-3592    

DOI:10.1002/bit.260100309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractA HeLa cell line was propagated in semicontinuous suspension culture, 85 liters final volume, and in continuous flow culture with a volume of 300 ml. or 5 liters in an autoclavable medium to which 8% calf serum had been added. A medium containing 0.1% Methocel and 2% calf serum was also tested. Maximum productivity was obtained at a dilution rate of 0.33 day−1with a cell density of about 1.0 × 106cells/ml. The same cell line was also infected withRubellavirus and the production of virus was followed at the 5‐liter cultivation l

ISSN:0006-3592    

DOI:10.1002/bit.260100310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY

摘要:

AbstractThe purpose of this experimental study was to examine the transient response of a chemostat‐type continuous culture ofEscherichia coliB to step changes in temperature by following transient limiting substrate concentration and calculating from it the transient growth rate. The transient response to step changes of temperature was tested for four different situations. In the first two cases, temperature was shifted down from 37 to 27°C., and 37 to 32°C. In the last two, it was shifted up from 32 to 37°C., and 27 to 37°C. When the temperature was shifted up, the growth rate increased rather rapidly to its transient maximum value and then decreased slowly until it, settled back into the steady‐state value. On the other hand, when the temperature was shifted down, the growth rate decreased relatively rapidly to its transient minimum and then it slowly increased and returned gradually to the steady‐state value. The magnitude of the transients was less than would be expected if the transient growth rates followed an Arrhenius

ISSN:0006-3592    

DOI:10.1002/bit.260100311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1968

数据来源: WILEY