Chitin and chitosan, typical marine polysaccharides as well as abundant biomass resources, are attracting a great deal of attention because of their distinctive biological and physicochemical characteristics. To fully explore the high potential of these specialty biopolymers, basic and application researches are being made extensively. This review deals with the fundamental aspects of chitin and chitosan such as the preparation of chitin and chitosan, crystallography, extent of N-acetylation, and some properties. Recent progress of their chemistry is then discussed, focusing on elemental modification reactions including acylation, alkylation, Schiff base formation and reductive alkylation, carboxyalkylation, phthaloylation, silylation, tosylation, quaternary salt formation, and sulfation and thiolation.

Chitin and Chitosan: Functional Biopolymers from Marine Crustaceans

Use of natural biopolymers for diversified applications in life sciences has several advantages, such as availability from replenishable agricultural or marine food resources, biocompatibility, biodegradability, therefore leading to ecological safety and the possibility of preparing a variety of chemically or enzymatically modified derivatives for specific end uses. Polysaccharides, as a class of natural macromolecules, have the tendency to be extremely bioactive, and are generally derived from agricultural feedstock or crustacean shell wastes. Cellulose, starch, pectin, etc. are the biopolymers derived from the former while chitin and chitosan are obtained from the latter. In terms of availability, chitin is next to cellulose, available to the extent of over 10 gigatons annually. The application potential of chitosan, a deacetylated derivative of chitin, is multidimensional, such as in food and nutrition, biotechnology, material science, drugs and pharmaceuticals, agriculture and environmental protection, and recently in gene therapy too. The net cationicity as well as the presence of multiple reactive functional groups in the molecule make chitosan a sought-after biomolecule. The latter offers scope for manipulation for preparing a broad spectrum of derivatives for specific end use applications in diversified areas. The biomedical and therapeutic significance of chitin/chitosan derivatives is a subject of significant concern to many all over the world. An attempt is made in this overview to consolidate some of the recent findings on the biorelated application potential of chitosan and its derivatives.

Chitin/chitosan: modifications and their unlimited application potential—an overview

in them. The presence of these groups may allow the plant to maintain high levels of storage protein synthesis despite variations in sulfur availability. The strict tissue specificity of seed storage protein synthesis contrasts with that of tuber storage proteins, which may be synthesized in vegetative tissues under unusual conditions (for example, in vitro or after removal of tubers) (Shewry, 1995). A second common property of seed storage proteins is their presence in the mature seed in discrete deposits called protein bodies, whose origin has been the subject of some dispute and may in fact vary both between and within species. Finally, all storage protein fractions are mixtures of components that exhibit polymorphism both within single genotypes and among genotypes of the same species. This polymorphism arises from the presence of multigene families and, in some cases, proteolytic processing and glycosylation.

/pdf/seed-storage-proteins-structures-and-biosynthesis-53ys18yj61.pdf

Seed storage proteins: structures and biosynthesis.

Nitrogen assimilation is a vital process controlling plant growth and development. Inorganic nitrogen is assimilated into the amino acids glutamine, glutamate, asparagine, and aspartate, which serve as important nitrogen carriers in plants. The enzymes glutamine synthetase (GS), glutamate synthase (GOGAT), glutamate dehydrogenase (GDH), aspartate aminotransferase (AspAT), and asparagine synthetase (AS) are responsible for the biosynthesis of these nitrogen-carrying amino acids. Biochemical studies have revealed the existence of multiple isoenzymes for each of these enzymes. Recent molecular analyses demonstrate that each enzyme is encoded by a gene family wherein individual members encode distinct isoenzymes that are differentially regulated by environmental stimuli, metabolic control, developmental control, and tissue/cell-type specificity. We review the recent progress in using molecular-genetic approaches to delineate the regulatory mechanisms controlling nitrogen assimilation into amino acids and to define the physiological role of each isoenzyme involved in this metabolic pathway.

The molecular-genetics of nitrogen assimilation into amino acids in higher plants

Controlled functionalization of the polysaccharide chitin

Diacylglycerol acyltransferase in maturing safflower seeds: its influences on the fatty acid composition of triacylglycerol and on the rate of triacylglycerol synthesis.

Using a rice maturing seed pUC9 expression library, we isolated a cDNA clone corresponding to 10 kDa sulfurrich prolamin by immunoscreening. A longer cDNA clone was obtained from a λgtll library by plaque hybridization using this 32P-labeled cDNA as a probe. A polypeptide sequence composed of 134 amino acids was deduced from the nucleotide sequence. A 24 amino acid signal peptide was assigned by computer calculation for the membrane spanning region and Edman sequencing of the purified mature polypeptide. Remarkably, 20% of methionine and 10% of cysteine were found in the mature polypeptide as well as high contents of glutamine, and hydrophobic amino acids. Part of the amino acid sequence was homologous with a conserved cysteine-rich region found in other plant prolamins. Two repeats of amino acid sequence were found in the polypeptide.

cDNA cloning of an mRNA encoding a sulfur-rich 10 kDa prolamin polypeptide in rice seeds

Atsushi Sakamoto i, Masahiro Ogawa 3, Takehiro Masumura l, Daisuke Shibata 1, Go Takeba 2, Kunisuke Tanaka 1 and Shoji Fujii 1 1Laboratory of Biochemistry, Faculty of Agriculture, Kyoto Prefectural University, Shimogamo, Kyoto 606, Japan; 2Laboratory of Applied Biology, Faculty of Living Science, Kyoto Prefectural University, Shimogamo, Kyoto 606, Japan; 3Laboratory of Food Production, The Research Institute for Food Science, Kyoto University, Ufi, Kyoto 611, Japan

Three cDNA sequences coding for glutamine synthetase polypeptides in Oryza sativa L.

A 20,000 X g particulate preparation isolated from maturing safflower seeds catalyzed the acylation of 1-acyl-sn-glycerol 3-phosphate with acyl-CoA to form phosphatidate. The specific activity of the reaction exceeded 200 nmol min-1 mg protein-1. Although this preparation was also capable of catalyzing the acylation of sn-glycerol 3-phosphate with acyl-CoA, the hydrolysis of phosphatidate, and the acylation of 1,2-diacylglycerol, phosphatidate was the only major product when the preparation was incubated with 1-acyl-glycerol-3-P and acyl-CoA. The enzyme responsible for this phosphatidate synthesis, 1-acyl-glycerol-3-P acyltransferase, showed a strict acyl-CoA specificity. The relative order of specificity for acyl-CoA was linoleoyl = oleoyl greater than palmitoleoyl greater than elaidoyl greater than cis-vaccenoyl greater than stearoyl = palmitoyl. This observation strongly suggests that the fatty acid composition of position 2 in phosphatidate synthesized in vivo primarily depends on both the acyl-CoA specificity of the 1-acyl-glycerol-3-P acyltransferase and the fatty acid composition of the acyl-CoA pool in the cell. Thus, the absence of saturated fatty acids at position 2 of safflower triacylglycerol may be explained in terms of the acyl-CoA specificity of the 1-acyl-glycerol-3-P acyltransferase. The fatty acid moiety esterified at position 1 of glycerol-3-P also affected the effectiveness of the reaction. The 1-acyl-glycerol-3-P acyltransferase utilized 1-acyl-glycerol-3-P molecular species in the following order of effectiveness: linoleoyl = oleoyl greater than palmitoyl. With a rise in incubation temperature, the initial rates of acylation with unsaturated acyl-CoA species increased more rapidly than those for saturated acyl-CoA species. A similar tendency was observed for saturated and unsaturated acyl acceptors. These data suggest that affinity of the acyltransferase for substrates may vary in response to changes in temperature, and that 1-acyl-glycerol-3-P acyltransferase may be involved in the alteration of the individual fatty acid compositions at positions 1 and 2 of glycerolipids in tissues grown at different temperatures. Based on these findings, further metabolism of 1-acyl-glycerol-3-P acyltransferase products could be the major factor determining the non-random distribution of fatty acids in safflower triacylglycerol.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1432-1033.1987.tb13342.x

1-Acyl-sn-glycerol-3-phosphate acyltransferase in maturing safflower seeds and its contribution to the non-random fatty acid distribution of triacylglycerol.

Rice prolamin extracted with 60 % (v/v) n-propanol from protein-rich rice bran was fractionated into individual polypeptides by SDS-polyacrylamide gel electrophoresis and isoelectric focusing. The prolamin polypeptides of 10, 13, and 16 kDa were acid hydrolized, and the amino acid composition of each polypeptide was analyzed. These prolamin polypeptides were rich in glutamic acid/glutamine and » * leucine but poor in lysine as reported previously for prolamins of many cereals. The 10 and 16 kDa polypeptides had a markedly high content of sulfur-containing amino acids.

https://www.jstage.jst.go.jp/article/bbb1961/53/2/53_2_513/_pdf

Shoji Fujii

Papers

Diacylglycerol acyltransferase in maturing safflower seeds: its influences on the fatty acid composition of triacylglycerol and on the rate of triacylglycerol synthesis.

cDNA cloning of an mRNA encoding a sulfur-rich 10 kDa prolamin polypeptide in rice seeds

Three cDNA sequences coding for glutamine synthetase polypeptides in Oryza sativa L.

1-Acyl-sn-glycerol-3-phosphate acyltransferase in maturing safflower seeds and its contribution to the non-random fatty acid distribution of triacylglycerol.

Amino Acid Composition of Rice Prolamin Polypeptides