Analysis of green kiwi fruit (Actinidia deliciosa cv. Hayward) proteinases by two-dimensional zymography and direct identification of zymographic spots by mass spectrometry

Effects of Green Kiwifruit Peel Extract on Sleep-Wake Profiles in Mice: A Polysomnographic Study Based on Electroencephalogram and Electromyogram Recordings

In the previous study, it was reported that green kiwifruit peel ethanol extract (GKPEE) increases sleep duration and decreases sleep latency in pentobarbital-treated mice. The pentobarbital-induced sleep test can be used to verify sleep quantity, which includes factors such as sleep duration and latency, but not sleep quality. In the present study, the sleep-promoting effects of GKPEE were investigated by the analysis of electroencephalogram (EEG) and electromyogram in mice and were compared with the results of diazepam (DZP), a representative sedative-hypnotic agent. The acute administration of GKPEE (250, 500 and 1000 mg/kg) increased the amount of non-rapid eye movement sleep (NREMS) and decreased sleep latency in a dose-dependent manner. The effect of GKPEE at 1000 mg/kg produced persistently significantly different results until the second hour of time-course changes. In particular, GKPEE did not produce any change in delta activity compared to DZP. Furthermore, sub-chronic administration (15 days) of GKPEE (500 mg/kg) continued sleep-promoting effects, whilst the EEG power density of NREMS did not show significant differences, indicating that there were no tolerance phenomena. Our findings suggest that GKPEE may be a promising natural sleep aid for treating sleep disorders. In addition, considering the number of by-products discarded each year by the food industry, the application of GKPEE here contributes to the utilization of processed kiwifruit by-products and can help to solve environmental problems.

Toward characterizing germination and early growth in the non-orthodox forest tree species Quercus ilex through complementary gel and gel-free proteomic analysis of embryo and seedlings

By using two complementary proteomics, gel-based and gel-free (shotgun) approaches, the protein profiles of the non-orthodox forest tree species Quercus ilex seeds during germination and early seedling growth have been compared. Proteins were extracted from embryo axis, radicle and shoot tissues at different developmental stages. Proteins were subjected to one- and two-dimensional gel electrophoresis. A multivariate analysis (PCA) revealed that SDS-PAGE clearly separated germination (0-24 h post-imbibition), postgermination (72-216 h post-imbibition) and early seedling growth stages (2 weeks post-imbibition). Image analysis of the two-dimensional gels revealed a total of 732 spots, 103 of which were significantly variable among developmental stages. After MALDI-TOF/TOF MS analysis, 90 spots were identified, belonging to six main functional categories: carbohydrate, amino acids, energy, and protein metabolism, biosynthesis of secondary metabolites, and redox processes. The gel-based approach disclosed important metabolic changes that occurred in the holm oak seed after the germination. However, few proteins were significantly altered during the germination period (from 0 h to 24 h post imbibition) and, because of that, a further shotgun analysis was therefore used to analyse changes in the protein profile during seed germination. Up to 1250 proteins could be confidently identified, with 153 being variable. They belonged to the main functional categories of carbohydrate, amino acids and secondary metabolism, protein degradation, and responses to abiotic stress. The accumulation of proteases and amino acids metabolism proteins in mature seeds can be reflecting the production of energy from the mobilization of storage proteins to start germination. These results, therefore, corroborate the hypothesis that the mature non-orthodox seeds of Q. ilex have all the machinery necessary for rapidly resuming metabolic activities and starting the germination process, in contrast to that occurs in orthodox seeds, which metabolic activity ceases in mature dry seeds. The use of a genus-specific database combined with the public Viridiplantae database improved the quality and quantity of protein identification in this orphan species. In addition, both proteomics approaches (gel-based and shotgun) were complementary, with shotgun increasing by over two-fold the coverage of the proteome analysed. Both approaches provided similar results and supported the same conclusions on the metabolic switch experienced by the seed upon germination. SIGNIFICANCE: The optimal seed germination is a prerequisite for successful seedling establishment and plant vigour, being of great relevance in the case of crops and commercial woody plants. By using a complementary gel-based and gel-free proteomic strategy we have study the protein profiles of the non-orthodox forest tree species Quercus ilex seeds during germination and early seedling growth. The contribution of this work is of great importance, due to the complemented proteomic approaches giving similar clues to the metabolic state of the mature Q. ilex seed before the germination starts, and the metabolic switch experienced by the imbibed acorn until the seedling is established.

Two-dimensional zymography differentiates gelatinase isoforms in stimulated microglial cells and in brain tissues of acute brain injuries

Excessive activation of gelatinases (MMP-2/-9) is a key cause of detrimental outcomes in neurodegenerative diseases. A single-dimension zymography has been widely used to determine gelatinase expression and activity, but this method is inadequate in resolving complex enzyme isoforms, because gelatinase expression and activity could be modified at transcriptional and posttranslational levels. In this study, we investigated gelatinase isoforms under in vitro and in vivo conditions using two-dimensional (2D) gelatin zymography electrophoresis, a protocol allowing separation of proteins based on isoelectric points (pI) and molecular weights. We observed organomercuric chemical 4-aminophenylmercuric acetate-induced activation of MMP-2 isoforms with variant pI values in the conditioned medium of human fibrosarcoma HT1080 cells. Studies with murine BV-2 microglial cells indicated a series of proform MMP-9 spots separated by variant pI values due to stimulation with lipopolysaccharide (LPS). The MMP-9 pI values were shifted after treatment with alkaline phosphatase, suggesting presence of phosphorylated isoforms due to the proinflammatory stimulation. Similar MMP-9 isoforms with variant pI values in the same molecular weight were also found in mouse brains after ischemic and traumatic brain injuries. In contrast, there was no detectable pI differentiation of MMP-9 in the brains of chronic Zucker obese rats. These results demonstrated effective use of 2D zymography to separate modified MMP isoforms with variant pI values and to detect posttranslational modifications under different pathological conditions.

Active actinidin retains function upon gastro-intestinal digestion and is more thermostable than the E-64-inhibited counterpart

BACKGROUND

Actinidin is a cysteine protease and major allergen from kiwi fruit. When purified under specific native conditions, actinidin preparations from fresh kiwi fruit contain both an active and inactive form of this enzyme. In this study, biochemical and immunological properties upon simulated gastro-intestinal digestion, as well as thermal stability, were investigated for both active and E-64-inhibited actinidin.

RESULTS

Active actinidin retained its primary structure and proteolytic activity after 2 h of simulated gastric digestion, followed by 2 h of intestinal digestion, as assessed by SDS-PAGE, zymography and mass spectroscopy. Immunological reactivity of active actinidin was also preserved, as tested by immunoelectrophoresis. The E-64 inhibited actinidin was fully degraded after 1 h of pepsin treatment. Differential scanning calorimetry showed that active actinidin has one transition maximum temperature (Tm ) at 73.9°C, whereas in the E-64-actinidin complex the two actinidin domains unfolded independently, with the first domain having a Tm value of only 61°C.

CONCLUSION

Active actinidin is capable of reaching the intestinal mucosa in a proteolytically active and immunogenic state. Inhibitor binding induces changes in the actinidin molecule that go beyond inhibition of proteolytic activity, also influencing the digestion stability and Tm values of actinidin, features important in the characterisation of food allergens.

The relative anthelmintic efficacy of plant-derived cysteine proteinases on intestinal nematodes

We examined the in vitro and in vivo efficacy of plant cysteine proteinases (CPs) derived from pineapple (Ananas comosus) and kiwi fruit (Actinidia deliciosa), and compared their efficacy as anthelmintics to the known effects of CPs from the latex of papaya (Carica papaya) against the rodent intestinal nematode, Heligmosomoides bakeri. Both fruit bromelain and stem bromelain had significant in vitro detrimental effects on H. bakeri but in comparison, actinidain from kiwi fruit had very little effect. However, in vivo trials indicated far less efficacy of stem bromelain and fruit bromelain than that expected from the in vitro experiments (24.5% and 22.4% reduction in worm burdens, respectively) against H. bakeri. Scanning electron microscopy revealed signs of cuticular damage on worms incubated in fruit bromelain, stem bromelain and actinidain, but this was far less extensive than on those incubated in papaya latex supernatant. We conclude that, on the basis of presently available data, CPs derived from pineapples and kiwi fruits are not suitable for development as novel anthelmintics for intestinal nematode infections.

What are the proteolytic enzymes of honey and what they do tell us? A fingerprint analysis by 2-D zymography of unifloral honeys

Honey is a sweet and healthy food produced by honeybees (Apis mellifera L.) from flower nectars. Using bidimensional zymography, we have detected the, until now unrevealed, proteolytic activities present in row honey samples. The resulting zymograms were specific for each type of the four unifloral honey under study, and enzymes were identified as serine proteases by the use of specific inhibitors. Further, using bidimensional electrophoresis, we have shown that honey proteases are able to degrade the major Royal Jelly proteins and in particular MRPJ-1, the protein that promotes queen differentiation in honeybees. Our findings open new perspectives for the better understanding of honeybee development, social behaviour and role in honey production. The now discovered honey proteases may influence honey properties and quality, and bidimensional zymograms might be useful to distinguish between different honey types, establish their age and floral origin, and allow honey certification.

Green and gold kiwifruit peel ethanol extracts potentiate pentobarbital-induced sleep in mice via a GABAergic mechanism

Kiwifruit is one of the most popular fruits worldwide, and it has various biological properties, including antioxidant, anti-allergic, and cardiovascular protective effects. The peel of kiwifruit, which is a by-product of processing, is a good source of flavonoids; however, its bioactivity has not been widely investigated. In this study, we evaluated the hypnotic effects of green (GRPE, Actinidia deliciosa) and gold (GOPE, Actinidia chinensis) kiwifruit peel ethanol extracts and their solvent fractions, and the possible underlying mechanisms. Oral GRPE and GOPE administration (125-1000mg/kg) produced a dose-dependent decrease in sleep latency and an increase in sleep duration in pentobarbital-treated mice. Among three different solvent fractions of GRPE and GOPE, ethyl acetate (EA) fractions had the greatest effect on sleep duration at 250mg/kg. The total flavonoid contents of solvent fractions were proportional to sleep duration. Like diazepam (a GABA(A)-benzodiazepine (BZD) receptor agonist), the hypnotic effects of GRPE, GOPE, and their EA fractions were fully inhibited by flumazenil (a GABA(A)-BZD receptor antagonist). These results suggest that potentiation effects of GRPE and GOPE on pentobarbital-induced sleep in mice may be modulated by a GABAergic mechanism.

Mapping, complementation, and targets of the cysteine protease actinidin in kiwifruit

Cysteine proteases (CPs) accumulate to high concentration in many fruit, where they are believed to play a role in fungal and insect defense. The fruit of Actinidia species (kiwifruit) exhibit a range of CP activities (e.g. the Actinidia chinensis variety YellowA shows less than 2% of the activity of Actinidia deliciosa variety Hayward). A major quantitative trait locus for CP activity was mapped to linkage group 16 in a segregating population of A. chinensis. This quantitative trait locus colocated with the gene encoding actinidin, the major acidic CP in ripe Hayward fruit encoded by the ACT1A-1 allele. Sequence analysis indicated that the ACT1A locus in the segregating A. chinensis population contained one functional allele (A-2) and three nonfunctional alleles (a-3, a-4, and a-5) each containing a unique frameshift mutation. YellowA kiwifruit contained two further alleles: a-6, which was nonfunctional because of a large insertion, and a-7, which produced an inactive enzyme. Site-directed mutagenesis of the act1a-7 protein revealed a residue that restored CP activity. Expression of the functional ACT1A-1 cDNA in transgenic plants complemented the natural YellowA mutations and partially restored CP activity in fruit. Two consequences of the increase in CP activity were enhanced degradation of gelatin-based jellies in vitro and an increase in the processing of a class IV chitinase in planta. These results provide new insight into key residues required for CP activity and the in vivo protein targets of actinidin.

2-D zymographic analysis of Broccoli (Brassica oleracea L. var. Italica) florets proteases: follow up of cysteine protease isotypes in the course of post-harvest senescence

Zymographic analysis of Broccoli florets (Brassica oleracea L. var. Italica) revealed the presence of acidic metallo-proteases, serine proteases and cysteine proteases. Under conditions which were denaturing for the other proteases, the study was restricted to cysteine proteases. 2-D zymography, a technique that combines IEF and zymography was used to show the presence of 11 different cysteine protease spots with molecular mass of 44 and 47-48kDa and pIs ranging between 4.1 and 4.7. pI differences could be ascribed to different degrees of phosphorylation that partly disappeared in the presence of alkaline phosphatase. Post-harvest senescence of Broccoli florets was characterized by decrease in protein and chlorophyll contents and increase of protease activity. In particular, as determined by 2-D zymography, the presence of cysteine protease clearly increased during senescence, a finding that may represent a useful tool for the control of the aging process.