Amberlite IRA 900 versus calcium alginate in immobilization of a novel,engineered β-fructofuranosidase for short-chain fructooligosaccharide synthesis from sucrose

The immobilization of β-fructofuranosidase for short-chain fructooligosaccharide (scFOS) synthesis holds the potential for a more efficient use of the biocatalyst. However, the choice of carrier and immobilization technique is a key to achieving that efficiency. In this study, calcium alginate (CA), Amberlite IRA 900 (AI900) and Dowex Marathon MSA (DMM) were tested as supports for immobilizing a novel engineered β-fructofuranosidase from Aspergillus japonicus for scFOS synthesis. Several immobilization parameters were estimated to ascertain the effectiveness of the carriers in immobilizing the enzyme. The performance of the immobilized biocatalysts are compared in terms of the yield of scFOS produced and reusability. The selection of carriers and reagents was motivated by the need to ensure safety of application in the production of food-grade products. The CA and AI900 both recorded impressive immobilization yields of 82 and 62%, respectively, while the DMM recorded 47%. Enzyme immobilizations on CA, AI900 and DMM showed activity recoveries of 23, 27, and 17%, respectively. The CA, AI900 immobilized and the free enzymes recorded their highest scFOS yields of 59, 53, and 61%, respectively. The AI900 immobilized enzyme produced a consistent scFOS yield and composition for 12 batch cycles but for the CA immobilized enzyme, only 6 batch cycles gave a consistent scFOS yield. In its first record of application in scFOS production, the AI900 anion exchange resin exhibited potential as an adequate carrier for industrial application with possible savings on cost of immobilization and reduced technical difficulty.     

Presence of cyclopiazonic acid in kodo millet (Paspalum scrobiculatum) causing ‘kodua poisoning’ in man and its production by associated fungi

Cyclopiazonic acid was isolated and identified from a sample of kodo millet seed that caused symptoms of kodua poisoning in man. The extract of the toxic grain when injected intraperitoneally into mice produced symptoms of depression and complete loss of mobility. The seed was infected by Aspergillus flavus and A. tamarii and both fungi produced cyclopiazonic acid. This is the first report of the association of a mycotoxin with kodua poisoning and of A. tamarii with mycotoxicoses.     

Analysis of the amino acid sequences of plant Bowman-Birk inhibitors

Plant seeds contain a large number of protease inhibitors of animal, fungal, and bacterial origin. One of the well-studied families of these inhibitors is the Bowman-Birk family(BBI). The BBIs from dicotyledonous seeds are 8K, double-headed proteins. In contrast, the 8K inhibitors from monocotyledonous seeds are single headed. Monocots also have a 16K, double-headed inhibitor. We have determined the primary structure of a Bowman-Birk inhibitor from a dicot, horsegram, by sequential edman analysis of the intact protein and peptides derived from enzymatic and chemical cleavage. The 76-residue-long inhibitor is very similar to that ofMacrotyloma axillare. An analysis of this inhibitor along with 26 other Bowman-Birk inhibitor domains (MW 8K) available in the SWISSPROT databank revealed that the proteins from monocots and dicots belong to related but distinct families. Inhibitors from monocots show larger variation in sequence. Sequence comparison shows that a crucial disulphide which connects the amino and carboxy termini of the active site loop is lost in monocots. The loss of a reactive site in monocots seems to be correlated to this. However, it appears that this disulphide is not absolutely essential for retention of inhibitory function. Our analysis suggests that gene duplication leading to a 16K inhibitor in monocots has occurred, probably after the divergence of monocots and dicots, and also after the loss of second reactive site in monocots. S. Selvaraj is on leave from Department of Physics, Bharathidasan University, Tiruchirapalli 620 024, Tamilnadu, India Correspondence to: M.R.N. Murthy     

Evidence for altered structure and impaired mitochondrial electron transport function in selenium deficiency

Selenium (Se) deficiency in the experimental models,Coturnix coturnix japonica andCorcyra cephalonica, resulted in impaired mitochondrial substrate oxidations and lowered thiol levels. Studies with respiratory inhibitors confirmed reduced mitochondrial electron transport enzyme activities, especially at cytochromec oxidase (COX), the terminal segment. Enhanced mitochondrial lipid peroxidation in Se deficiency was more pronounced in the heart tissue of the quail compared to other tissues. Glutathione peroxidase (GSH-Px) activity toward H₂O₂ and cumene hydroperoxide were generally low in the insect muscle tissue and activity toward H₂O₂ was maximal in the quail heart mitochondria that was not very sensitive to Se status. Lowered COX activity in Se deficiency was more directly correlated with the increased level of lipid peroxidation than with the GSH-Px activity measured, suggestive of Se mediated protective mechanisms independent of GSH-Px. Electron microscopic observations revealed structural changes such as loss of cristae with proliferative and degenerative changes of the mitochondria in Se deficiency. Involvement of Se in maintaining structure and functional efficiency of mitochondria is evident from the present study.     

Application of recombinant DNA technology to plant protection: molecular approaches to engineering virus resistance in crop plants

Developments in plant tissue culture, plant transformation and regeneration, and improvements in techniques to isolate and manipulate viral genes have led to the exploitation of the concept of cross protection: turning the virus onto itself and controlling it with its own genes. By introducing and expressing genes of viral origin in crop plants, scientists have engineered resistance to several plant viruses. Some of the approaches, used singly or in combination, include expression of viral-coat protein, untranslatable sense or antisense RNA, satellite RNA, virusspecific neutralizing antibody genes, plant viral replicase, protease or movement proteins and defective, interfering RNA. All of these approaches have resulted in manifestation of virus resistance to varying degrees in several commercially important crop plants. This review summarizes the recent advances in engineering virus resistance using the above approaches, and lists specific examples of their use in cultivated crop plants of economic importance.H.R. Pappu and C.L. Niblett are with the Plant Pathology Department, University of Florida. Gainesville, FL 32611-0680, USA; R.F. Lee is with the Citrus Research and Education Center, University of Florida, Lake Alfred, FL 33850, USA. Florida Agricultural Experiment Station Journal Series No. R-04558.     

Mevalonate decarboxylation in lemon grass leaves

The activity of mevalonate-5-pyrophosphate (MVAPP) decarboxylase was assayed in the extracts of green leaves of lemon grass. The enzyme was found to be exclusively cytosolic, had a pH optimum of 6.0 and had a specific requirement for ATP; Mg²⁺ was required and Mn²⁺ could replace it partially. The phenolic compounds, p-coumaric acid, protocatechuic acid, ferulic acid and phloroglucinol carboxylic acid inhibited the activity.     

Identification and partial characterization of two species-specific repeat families in the great millet (Sorghum vulgare,Poaceae) genome

The 1.4 kbp Xba I and the 1.3 kbp EcoRI repeat families in great millet were partially characterized with respect to their genomic distribution and their homology with the EcoRI and Xba I families of five other millet DNAs. The digestions of great millet DNA using increasing amounts of the two enzymes show that these two families are disperse in nature. The hybridization of these two families to the genomic digests of great millet indicates that they are arranged in a clustered and scrambled manner. Similarly, the hybridization with the EcoRI and Xba I digests of five other millet DNAs reveals the speciesspecific nature of these two repeat families. The latter also hybridize to the total repetitive fraction of great millet isolated at a highly stringent temperature of 75°C suggesting that the members of these two families are probably largely homogeneous.