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1.
The structure of Eubacterium nodatum cell wall peptidoglycan was investigated. The peptide subunit of E. nodatum peptidoglycan has the following structure: L-Ala-D-Glu (Gly)-L-Orn-D-Ala. The carboxyl group of alanine occupying position 4 is attached to the -amino group of ornithine of an other subunit by the cross-linking bridge L-Ala-L-Ala-L-Orn. All glycine molecules are connected with the -carboxyl group of glutamic acid with the ratio being 0.5–1. The hydrolysis of E. nodatum peptidoglycan by the S. albus G enzyme proceeds primarily due to the activity of alanyl-alanine endopeptidase, ornithyl-ornithine endopeptidase, ornithyl-alanine endopeptidase, N-acetyl-muramyl-alanine amidase, N-acetylmuramidase and N-acetylglucosaminidase. 相似文献
2.
Zdenka Valinger Dina Keglević Mercedes Wrischer Radmila Naumski 《Archives of microbiology》1982,132(3):280-284
Purified cell walls, originating from penicillin-treated (3 g/ml, 1 h) and-untreated Brevibacterium divaricatum cells grown on complex (CM) and glucose minimal medium with (MM) or without (Ca-free MM) calcium carbonate, were isolated by two procedures. Electron micrographs and chemical analysis revealed no differences between identically isolated walls with respect to the presence or absence of either penicillin or calcium carbonate in the glucose growth medium. On the contrary, the appearance and peptidoglycan content of the walls was greatly dependent on the procedure used for their isolation and the walls isolated from the cells grown on complex medium contained more materials other than peptidoglycan. It was shown that the presence of calcium carbonate in the glucose minimal medium was essential for accumulation of large amounts of peptidoglycan chains into the medium. Penicillin-induced interruption of cell wall synthesis was prerequisite for manifestation of the calcium carbonate stimulating effect.Abbreviations CM
complex medium
- MM
chemically defined minimal medium based on glucose and containing calcium carbonate
- Ca-free MM
MM modified only by the omission of calcium carbonate
- ET-walls
Enzyme treated walls
- FPR-walls
French press-ruptured walls 相似文献
3.
Peter H. Seidl Anton H. Faller Renate Loider Karl-Heinz Schleifer 《Archives of microbiology》1980,127(3):173-178
Determination of the primary structure of the peptidoglycan of 15 strains of Oerskovia showed that three different peptidoglycan types occur. Oerskovia xanthineolytica strains contain the l-Lys-d-Ser--d-Asp type, whereas Oerskovia turbata strains show the new peptidoglycan types l-Lys-l-Thr--d-Asp or l-Lys-l-Thr--d-Glu, respectively. Research on the cytochromes of Oerskovia revealed the presence of a, b and c types. O. turbata can be clearly distinguished from O. xanthineolytica by the occurrence of cytochrome a
1 in cells, isolated from the stationary phase. The following conclusions were made: O. turbata and O. xanthineolytica can be clearly separated on the basis of different peptidoglycan types and cytochrome patterns. This distinction is in perfect correlation with the classical separation method of O. turbata and O. xanthineolytica on the basis of xanthine degradation. l-Lys-d-Ser--d-Asp peptidoglycan type does not only occur in O. xanthineolytica but also in some coryneform bacteria such as Corynebacterium manihot (Fiedler et al. 1970), Cellulomonas cartae (Stackebrandt et al. 1978; Stackebrandt and Kandler 1980), Brevibacterium fermentans and Nocardia cellulans.This paper is respectively dedicated to Professor Dr. O. Kandler, on the occasion of his 60th birthday 相似文献
4.
Valery V. Petrov Vladislav Yu. Artzatbanov Evgeny N. Ratner Anatoly I. Severin Igor S. Kulaev 《Archives of microbiology》1991,155(6):549-553
The action of the lysoamidase bacteriolytic complex on Staphylococcus aureus VKM B-209P cells has been studied to obtain protoplasts. The cells in the midlogarithmic phase were the most sensitive to lysoamidase action. It led to local destruction of cell wall due to hydrolysis of the peptidoglycan. Protoplast formation occurred in two steps in the presence of 1 M sucrose. First, osmotically fragile spheroplasts were formed. Then, the protoplasts were released from the destructed cell wall. The protoplast yield was about 80%. The protoplasts preserved the intact ultrastructure and were able to synthesize peptidoglycan fibrillae. Mainly the spheroplasts that maintained the cell-wall residues reversed into bacterial forms. The protoplasts had respiratory activity similar to cells. Respiration of cells and protoplasts was stimulated by various substrates. High rates of oxygen consumption were observed with -glycerophosphate and ethanol as substrates. 相似文献
5.
Cells of Clostridium sporosphaeroides which were grown on citrate contained citrate lyase and citrate lyase acetylating enzyme, but no detectable citrate synthase and citrate lyase deacetylase activities. Citrate lyase from C. sporosphaeroides was purified to homogeneity as judged by polyacrylamide gel electrophoresis and high performance liquid chromatography. In contrast to the enzyme from Clostridium sphenoides, the addition of l-glutamate was not necessary for activity and stabilization of the enzyme. The purified enzyme had a specific activity of 34 U/mg protein and was comparable to other citrate lyases with respect to its molecular weight and subunit composition. Electron microscopic investigations showed that similar to the lyase from C. sphenoides and in contrast to all other citrate lyases examined so far, the majority of the enzyme molecules was present in star form. 相似文献
6.
Chemical analyses on cell envelope polymers of the halophilic,phototrophic Rhodospirillum salexigens
Whole cells of Rhodospirillum salexigens, an obligatory halophilic bacterium, have a very low peptidoglycan content (0.17 mol muramic acid/mg cell dry weight) which is not sufficient to form a sacculus structure. The isolated peptidoglycan contains glucosamine: muramic acid: diaminopimelic acid: alanine: glutamic acid in molar ratios of 1:1:1:2:3. The degree of cross linking is 30%. A polysaccharide consisting of glucosamine, an unknown compound X and a 2-amino-2-deoxy-pentose (relative molar ratios; 1:2:1) was extracted into the water phase of phenol water extracts of whole cells. The polysaccharide co-sedimented with peptidoglycan when cell homogenates were centrifuged in the presence of 4% NaCl (100,000xg, 4 h) or on a sucrose gradient (20–60% sucrose, 28,000xg, 16 h) in the presence or absence of NaCl and/or EDTA.Lack of -hydroxy fatty acids and of 2-keto-3-deoxyoctonate in all phenol-water extract fractions as well as in the whole cell hydrolysate indicates the absence of common outer membrane lipopolysaccharide in R. salexigens. Removal of the cell surface layer exposed six proteins to labeling with radioactive iodine catalyzed by lactoperoxidase. These proteins are suggested to be constituents of the outer membrane of R. salexigens.Abbreviations Ala
alamine
- A2pm
diaminopimelic acid
- DDPT
dimethyl-3,3-dithiobispropionimidate dihydrochloride
- GlcN
glucosamine
- Glu
glutamic acid
- Gly
glycine
- His
histidine
- MurN
muramic acid
- SDS
sodium dodecyl sulfate 相似文献
7.
Synopsis Twenty-two plaques from six cases of multiple sclerosis were examined histochemically, with particular reference to demonstrating proteolytic activity by the gelatin-silver autogram method. Proteolytic activity was increased around plaques that were characterized as active (i.e. with increased cell population and NADH dehydrogenase activity at their edges). Inactive plaques showed little or no proteolytic activity. Proteolytic activity around active lesions could not be attributed to lipid-laden microglia: oligodendroglia or the myelin sheath are considered as alternative sources. Acid phosphatase and non-specific cholinesterase were mainly localized in lipid-laden microglia and the activity of these two enzymes was not otherwise prominent around active plaques. The oligodendroglia from unaffected white matter were found not to contain either of these enzymes. In view of previous observations that proteolytic enzymes causein vitro myelin breakdown and are also implicated in Wallerian degeneration, it is suggested that local proteolysis may be an initiating factor in the demyelinating process of multiple sclerosis.Research Associate supported by the British Multiple Sclerosis Society 相似文献
8.
Shizufumi Ebihara Keiko Uchiyama Itsuki Oshima 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1984,154(1):59-69
Summary The roles of the pineal organ and the eye in the control of circadian locomotor rhythmicity were studied in the pigeon (Columba livia). Neither pinealectomy nor blinding abolished the circadian rhythms in constant dim light conditions (LLdim). All the pinealectomized birds and the blinded birds entrained to light-dark (LD) cycles with no discernible anticipatory activity. However, the birds which had been both pinealectomized and blinded showed no circadian rhythms in prolonged LLdim. These birds entrained to LD cycles with anticipatory activity and showed residual rhythmicity for a while after transfer from LD cycles to LLdim. Continuous administration of melatonin induced suppression of the circadian rhythms and reduced total amount of locomotor activity in LLdim. These results suggest that not only the pineal organ but also the eye (perhaps the retina) is involved in the pigeon's circadian system.Abbreviations
NAT
N-acetyltransferase
-
LLdim
constant dim light
-
cadian period
-
SCN
suprachiasmatic nucleus
-
circadian activity time
-
LD
light-dark 相似文献
9.
Summary Embryoless wheat (Triticum aestivum L.) half-seeds on incubation with gibberellic acid (GA3) showed a 2- to 2.5fold stimulation of monophenolase activity. The enzyme activity was not released into the incubation medium in GA3-treated half-seeds. The effect of GA3 was counteracted by the addition of abscisic acid (ABA) to the half-seeds. Adenosine-3,5-cyclic monophosphate and its structural analogues were ineffective in increasing the monophenolase activity. Actinomycin D and cycloheximide showed no inhibitory effecton the monophenolase activity in controls as well as in GA3-treated half-seeds, but on the contrary caused a 2- to 3fold stimulation of enzyme activity similar to that observed in endosperm treated with GA3 alone. However, there was no additive or synergistic enhancement of monophenolase activity when GA3 was tested in combination with cycloheximide or actinomycin D. GA3- or cyclic AMP-treated half-seeds showed no stimulation of o-diphenolase activity. 相似文献
10.
Jäger Szilvia Brumbauer Anikó Fehér Erika Réczey Kati Kiss László 《World journal of microbiology & biotechnology》2001,17(5):455-461
-D-Glucosidase enzymes (-D-glucoside glucohydrolase, EC 3.2.1.21) from different Aspergillus strains (Aspergillus phoenicis, A. niger and A. carbonarius) were examined with respect to the enzyme production of the different strains using different carbon sources and to the effect of the pH and temperature on the enzyme activity and stability. An efficient and rapid purification procedure was used for purifying the enzymes. Kinetic experiments were carried out using p-nitrophenyl -D-glucopyranoside (pNPG) and cellobiose as substrates. Two different fermentation methods were employed in which the carbon source was glucose or wheat bran. Aspergillus carbonarius proved to be the less effective strain in -glucosidase production. Aspergillus phoenicis produced the highest amount of -glucosidase on glucose as carbon source however on wheat bran A. niger was the best enzyme producer. Each Aspergillus strain produced one single acidic -glucosidase with pI values in the range of pH 3.52–4.2. There was no significant difference considering the effect of the pH and temperature on the activity and stability among the enzymes from different origins. The enzymes examined have only -glucosidase activity. The kinetic parameters showed that all enzymes hydrolysed pNPG with higher efficiency than cellobiose. This shows that hydrophobic interaction plays an important role in substrate binding. The kinetic parameters demonstrated that there was no significant difference among the enzymes from different origins in hydrolysing pNPG and cellobiose as the substrates. 相似文献
11.
Karin Schubert Dieter Reiml Jean-Pierre Accolas Franz Fiedler 《Archives of microbiology》1993,160(3):222-228
The primary structure of the peptidoglycan and the teichoic acids of two coryneform isolates from the surface flora of French cooked cheeses, CNRZ 925 and CNRZ 926, have been determined. In the peptidoglycan, meso-diaminopimelic acid was localized in position three of the peptide subunit. It contained an d-glutamyl-d-aspartyl interpeptide bridge, connecting meso-diaminopimelic acid and d-alanine residues of adjacent peptide subunits. The -carboxyl group of d-glutamic acid in position two of peptide subunits was substituted with glycine amide. The teichoic acid pattern and composition differed between the strains: both contained an erythritol teichoic acid and strain CNRZ 925 also contained an N-acetylglucosaminylphosphate polymer. The erythritol teichoic acids differed in terms of the quality and quantity of substituents, but they both had N,N-diacetyl-2,3-diamino-2,3-dideoxyglucuronic acid in common.Abbreviations DNP
dinitrophenyl
- Ery
erythritol
- Gal
galactose
- GlcN
glucosamine
- GlcNAc
N-acetylglucosamine
- GlcUANAc2
N,N-diacetyl-2,3-diamino-2,3-dideoxyglucuronic acid
- Hex UANAc2
N,N-diacetyl-2,3-diamino-2,3-dideoxyhexuronic
- acid
m-Dpm, meso-diaminopimelic acid
- Mur
muramic acid
- MurNAc
N-acetylmuramic acid 相似文献
12.
Thomas A. Helmchen Debashish Bhattacharya Michael Melkonian 《Journal of molecular evolution》1995,41(2):203-210
Glaucocystophyte algae (sensu Kies, Berl. Deutsch. Bot. Ges. 92, 1979) contain plastids (cyanelles) that retain the peptidoglycan wall of the putative cyanobacterial endosymbiont; this and other ultrastructural characters (e.g., unstacked thylakoids, phycobilisomes) have suggested that cyanelles are primitive plastids that may represent undeveloped associations between heterotrophic host cells (i.e., glaucocystophytes) and cyanobacteria. To test the monophyly of glaucocystophyte cyanelles and to determine their evolutionary relationship to other plastids, complete 16S ribosomal RNA sequences were determined for Cyanophora paradoxa, Glaucocystis nostochinearum, Glaucosphaera vacuolata, and Gloeochaete wittrockiana. Plastid rRNAs were analyzed with the maximum-likelihood, maximumparsimony, and neighbor joining methods. The phylogenetic analyses show that the cyanelles of C. paradoxa, G. nostochinearum, and G. wittrockiana form a distinct evolutionary lineage; these cyanelles presumably share a monophyletic origin. The rDNA sequence of G. vacuolata was positioned within the nongreen plastid lineage. This result is consistent with analyses of nuclear-encoded rRNAs that identify G. vacuolata as a rhodophyte and support its removal from the Glaucocystophyta. Results of a global search with the maximumlikelihood method suggest that cyanelles are the first divergence among all plastids; this result is consistent with a single loss of the peptidoglycan wall in plastids after the divergence of the cyanelles. User-defined tree analyses with the maximum-likelihood method indicate, however, that the position of the cyanelles is not stable within the rRNA phylogenies. Both maximumparsimony and neighbor-joining analyses showed a close evolutionary relationship between cyanelles and nongreen plastids; these phylogenetic methods were sensitive to inclusion/exclusion of the G. wittrockiana cyanelle sequence. Base compositional bias within the G. wittrockiana 16S rRNA may explain this result. Taken together the phylogenetic analyses are interpreted as supporting a near-simultaneous radiation of cyanelles and green and nongreen plastids; these organelles are all rooted within the cyanobacteria.Correspondence to: D. Bhattacharya 相似文献
13.
Hirohiko Shimizu Gakuzo Tamura Kei Arima 《Bioscience, biotechnology, and biochemistry》2013,77(7):1485-1492
The intact globular cell wall peptidoglycan was prepared from Micrococcus lysodeikticus without any mechanical disruption. The purification procedure consists mainly of proteolytic digestion and extractions with hot 5% TCA and with 0.01 N NaOH. The purified preparation showed an amphoteric, heteroporous three-dimensional network structure of the peptidoglycan, which amounted to 77% of the dry weight of the preparation, retaining the chemical and morphological integrity as judged by an electron microscopic observation and chemical analyses. 相似文献
14.
Christina Scha¨ffer Norbert Mu¨ller Pravat K. Mandal Rudolf Christian Sonja Zayni Paul Messner 《Glycoconjugate journal》2000,17(10):681-690
The peptidoglycan, the secondary cell wall polymer (SCWP), and the surface layer (S-layer) glycoprotein are the major glycosylated cell wall components of Paenibacillus alvei
CCM 2051. In this report, the complete structure of the SCWP, its linkage to the peptidoglycan layer, and its physicochemical properties have been investigated. From the combined evidence of chemical and structural analyses together with one- and two-dimensional nuclear magnetic resonance spectroscopy, the following structure of the SCWP-peptidoglycan complex is proposed:[(Pyr4,6)--D-Manp
NAc-(14)--D-Glcp
NAc-(13)]ñ11-(Pyr4,6)--D-Manp
NAc-(14)--D-Glcp
NAc-(1O)-PO2-O-PO2-(O6)-MurNAc-Each disaccharide unit is substituted by 4,6-linked pyruvic acid residues. Under mild acidic conditions, up to 50% of them are lost, leaving non-substituted ManNAc residues. The anionic glycan chains constituting the SCWP are randomly linked via pyrophosphate groups to C-6 of muramic acid residues of the peptidoglycan layer. 31P NMR reveals two signals that, as a consequence of micelle formation, experience different line broadening. Therefore, their integral ratio deviates significantly from 1:1. By treatment with ethylenediaminetetraacetic acid, sodium dodecyl sulfate, and sonication immediately prior to NMR measurement, this ratio approaches unity. The reversibility of this behavior corroborates the presence of a pyrophosphate linker in this SCWP-peptidoglycan complex.In addition to the determination of the structure and linkage of the SCWP, a possible scenario for its biological function is discussed. 相似文献
15.
Infection of mucosal surfaces by N. gonorrhoeae and N. meningitidis may result in inflammation indicating potential injury to host cells. We used human fallopian tube organ cultures (FTOC) and human nasopharyngeal organ cultures (NPOC) to study the mechanisms by which gonococci and meningococci damage human mucosal surfaces. Early in the course of FTOC infected with gonococci and NPOC infected with meningococci, damage was most apparent to ciliary activity. Loss of ciliary activity was accompanied by sloughing of ciliated cells. The damage to ciliated cells was not associated with attachment of gonococci or meningococci to these cells or the presence of organisms within ciliated cells. Infection with the commensal N. subflava did not result in significant damage to human FTOC or NPOC ciliary activity. LPS appears to be a major toxin of gonococci for human FTOC ciliated cells. Gonococcal peptidoglycan fragments also damage FTOC ciliary activity. Both piliated (P+) and nonpiliated (P-) gonococci and meningococci damage FTOC and NPOC ciliary activity, but P+ organisms damage ciliary activity more rapidly than P- organisms. Damage to FTOC ciliated cells was produced by <10 g/ml of purified gonococcal and meningococcal LPS. By 1–2h after exposure to LPS, vesicles containing LPS were distributed throughout the cytoplasm of ciliated cells. Polymyxin B neutralized LPS-induced damage, suggesting that the lipid A portion of LPS was the toxic moiety. In contrast, purified gonococcal and meningococcal LPS at 100 g/ml did not damage human NPOC or FTOC from rabbits, pigs and cows. These studies indicate that N. gonorrhoeae and possibly N. meningitidis damage ciliated epithelial celsl indirectly by release of toxins from the organisms. The differences in susceptibility of FTOC and NPOC to LPS may suggest changes in density of receptors for LPS and may help explain variation in severity of gonococcal and meningococcal interactions at different human mucosal surfaces. 相似文献
16.
The contribution of fungal enzymes to the digestion of leaves by Gammarus fossarum Koch (Amphipoda) 总被引:2,自引:0,他引:2
Felix Bärlocher 《Oecologia》1982,52(1):1-4
Summary Gut extracts of Gammarus fossarum liberated reducing substances (at pH values 7) and amino acids (pH7) from freshly shed oak leaves only after removal of soluble leaf phenols. When carboxymethylcellulose was used at a concentration equal to that of leaf cellulose, release of reducing substances was considerably higher. Fungal enzymes extracted from decomposing leaves were active against structural carbohydrates but showed no proteolytic activity. At low pH values, they retained their full activity in the presence of gut enzymes of G. fossarum, at higher pH values they were inhibited. Conditioned leaves released larger amounts of reducing substances and amino acids when exposed to gut enzymes. The improvement varies with the fungal species used for conditioning and with the length of the conditioning period. The digestibility of leaf carbohydrates and proteins reached separate peaks and then declined. Fungal carbohydrases ingested by G. fossarum retained some activity for up to 4h. 相似文献
17.
Patrizia Fuschiotti Maria C. Fioretti Luigina Romani Paolo Puccetti 《Cancer immunology, immunotherapy : CII》1989,29(2):139-143
Summary The relationship between induction of novel immunogenicity by xenogenizing chemicals and DNA-methylating activity in murine tumors was investigated at the clonal level in L1210Ha cells treated with 5-azacytidine, N-methyl-N-nitro-N-nitrosoguanidine (MNNG) or 1-(p-chlorophenyl)-3,3-dimethyltriazene (DM-Cl). Cells were exposed to the drugs in vitro, cloned by limiting dilution, and assayed for transplantation immunogenicity and 5-methylcytosine content. The results showed that 0% (0/29, 5-azacytidine), 6.8% (2/29, MNNG) and 87.5% (28/32, DM-Cl) of the resulting clones were highly immunogenic, as judged by their tumorigenicity in intact compared to immunodepressed hosts. Frequency distribution analysis of the 5-methylcytosine content of drug-treated and parental clones showed that the methylation pattern was not significantly modified by tumor exposure to either 5-azacytidine or MNNG, and the two immunogenic clones induced by MNNG had methylcytosine levels very close to the 50th percentile value. In contrast, the extent of DNA methylation was increased in the cells treated with DM-Cl, but no obvious association was found between methylation status and immunogenicity of the drug-treated clones. In four 5-azacytidine-treated clones that displayed little or no immunogenicity, additional rounds of drug exposure led to progressive DNA demethylation, but failed, as a rule, to enhance tumor cell immunogenicity. Taken together, the present data indicate that, at least for the examined tumor, immunogenic variants are generated by mutagen treatment at high (MNNG) or very high (DM-Cl) frequencies under conditions in which hypomethylation-induced antigen amplification is unlikely.This work was supported by Progetto Finalizzato Oncologia, C. N. R, Rome-Italy, grant no. 87.01423.44
Abbreviations used: MNNG, N-methyl-N-nitro-N-nitrosoguanidine; DM-Cl, 1-(p-chlorophenyl)-3,3-dimethyltriazene; MST, difference (days) between median survival times of intact and irradiated mice injected with the same cells. 相似文献
18.
Neil C. Bruce Clare J. Wilmot Keith N. Jordan Anna E. Trebilcock Lauren D. Gray Stephens Christopher R. Lowe 《Archives of microbiology》1990,154(5):465-470
A strain of Pseudomonas putida was isolated by selective enrichment with morphine that was capable of utilising morphine as a primary source of carbon and energy for growth. Experiments with whole cells showed that both morphine and codeine, but not thebaine, could be utilised. A novel NADP-dependent dehydrogenase, morphine dehydrogenase, was purified from crude cell extracts and was shown to be capable of oxidising morphine and codeine to morphinone and codeinone, respectively. This NADP-dependent morphine dehydrogenase was not observed in any other species of pseudomonads examined and was quite distinct from the -hydroxysteroid dehydrogenase found in Pseudomonas testosteroni, which had previously been shown to have activity against morphine. 相似文献
19.
Magdalena Wójcik Kamil Szala Ronald van Merkerk Wim J. Quax Ykelien L. Boersma 《Proteins》2020,88(11):1394-1400
Sortases are a group of enzymes displayed on the cell-wall of Gram-positive bacteria. They are responsible for the attachment of virulence factors onto the peptidoglycan in a transpeptidation reaction through recognition of a pentapeptide substrate. Most housekeeping sortases recognize one specific pentapeptide motif; however, Streptococcus pyogenes sortase A (SpSrtA WT) recognizes LPETG, LPETA and LPKLG motifs. Here, we examined SpSrtA's flexible substrate specificity by investigating the role of the β7/β8 loop in determining substrate specificity. We exchanged the β7/β8 loop in SpSrtA with corresponding β7/β8 loops from Staphylococcus aureus (SaSrtA WT) and Bacillus anthracis (BaSrtA WT). While the BaSrtA-derived variant showed no enzymatic activity toward either LPETG or LPETA substrates, the activity of the SaSrtA-derived mutant toward the LPETA substrate was completely abolished. Instead, the mutant had an improved activity toward LPETG, the preferred substrate of SaSrtA WT. 相似文献
20.
Post-translational proteolytic processing and the isolectins of lentil and other Viciae seed lectins
Electrospray mass spectrometry was used to identify precisely the proteolytic cleavage points within, and at the C-termini of, the proprotein forms of four Viciae lectins that give rise to their two-chain forms. The lectins examined were the pea and lentil lectins, favin and theLathyrus odoratus lectin, which represent each of the four genera in this tribe. The molecular mass data showed single -chain forms for each lectin, with masses consistent with the available sequence and glycopeptide data, indicating that each came from a single proprotein. In contrast, the pea, lentil andL. odoratus -chains occurred in as many as five forms, due to multiple C-terminal cleavage points. Only favin showed a single -chain form. The -chain mass data were again consistent with the sequence information available, except for the lenti lectin -chain which was re-determined by protein sequencing. The two isolectin forms of this protein were shown to arise from -chain species with and without residue Lys53. The mass spectrum of concanavalin A was also examined and both the single-chain form and the two fragment forms showed no evidence of C-terminal heterogeneity. 相似文献