Four Arabidopsis genes homologous to the membrane-associated progesterone binding protein (MAPR) were identified. MAPRs have previously been isolated from membrane preparations of porcine liver as proteins binding to progesterone. According to sequence alignment, each of the AtMAPRs, except AtMAPR2, was predicted to contain three domains; the N-terminal domain, except that of AtMAPR2, was predicted to accommodate a single transmembrane alpha-helix. A potentially interesting helical wheel motif SPX10FX2Y was found in the transmembrane domain. Proteins that may interact with AtMAPRs were found using the yeast two-hybrid system. AtMAPR2 and AtMAPR5△TM were found to associate with ubiquitin, where ubiquitination was involved in Aux/IAA modification. Sequence alignment indicated that AtMAPRs are distantly related to the Aux/IAA proteins. AtMAPR2 was also found to bind Myb3, a transcription factor that controls the expression of genes for the biosynthesis of phenylpropanoid. These results imply that AtMAPR may be a part of a plant hormone signaling pathway.

Sucrose phosphate synthase (SPS) is one of a number of sucrose-metabolizing enzymes that regulates the sucrose synthesis pathway. SPSs were purified from etiolated rice seedlings (ERS), green rice seedlings (GRS), rice grain suspension cells under osmotic stress (RGSO), and rice grain suspension cells under illumination (RGSI). A native molecular mass of ca. 420 and 520 kDa was found using native-PAGE. The SDS-PAGE analyses revealed SPSs to be homotetramers composed of subunits with a mass of 116-120 kDa. The maximum activity for SPSs was observed on the third day. As far as their biochemical characterization was concerned, the optimum pH of the enzyme reactions lay generally between 6-8, the optimum temperatures between 35-40°C. The ERS and RGSO SPS Km values for Fm 6-P and UDPG were 1.8 and 35mM, respectively. However, the GRS and RGSI SPS had similar Km values for Fm 6-P and UDPG of 1.5 and 28mM, respectively. GRS and RGSI SPS activities were allosterically regulated by Glc 6-P (activator) or Pi (inhibitor), but ERS and RGSO SPS had no effect. From their regulations and Km values two enzyme forms (SPS-I and SPS-II) could be discriminated in the rice. SPS-II was induced by illumination, but SPS-I by osmotic stress. All SPSs were activated by Mg(superscript 2+). The nucleotides AMP, ADP, ATP, UMP, UDP, GDP and UTP inhibited enzyme activity by about 25-50%. Thiol reagents became sensitized to the enzyme activity, but could be restored with DTT or β-ME. Glucose, galactose, glucosamine, maltose, and lactose activated the enzymes and were inhibited by δ-gluconolactone and mannose. SPSs were also inhibited by PCMBS, cibacron blue F3G-A, and DEP.

Sucrose phosphate synthase (SPS) is one of the key enzymes in the sucrose biosynthesis pathway. SPS was purified 40 fold from crude extract of sweet potato tuberous roots by the methods of batch elution from DEAE-Sephacel, PEG precipitation, omega -aminohexyl Sepharose 4B affinity and Mono Q union exchange chomatographies. The native- and SDS-PAGE analyses revealed SPS to have a native molecular mass of about 540 kDa, and it may therefore be homotetramer composed of subunit with a mass of 130-140 kDa. The isoelectric point of the purified enzyme as determined by IEF was 5.29. SPS fi-om the sweet potato tuberous root, which differs from the SPS of photosynthetic tissues, was not allosterically regulated by G6P and Pi. The Km for F6P and UDPG was 5.3 and 31.3 mM, respectively. The enzyme was activated by Mn2+, Mg2+, and Ca2+, while being inhibited by Hg2+ The nucleotides AMP, ADP, ATP, UMP, UDP, UTP, and TDP inhibited the enzyme about 30 similar to 50%. The enzyme was sensitive to sulfydryl reagents, but activity could be restored with DTT or beta -ME. The enzyme was activated by glucose, glucosamine, maltose, and lactose, but was inhibited by delta -gluconolactone. SPS could also be inhibited by PCMBS and Cibacron blue F3G-A.

The intra- and extracellular sugar contents, the activities of sucrose-metabolizing enzymes, and the metabolism of [U-(14)C] glucose in a pulse-chase experiment were compared between the normal and osmotically stressed (by 0.6 M sorbitol) sweet potato (Ipomoea batatas) suspension cells. The stress enhanced the levels of sucrose and sucrose phosphate synthase (SPS) activity. Northern blot analysis also showed that prolonged osmotic stress enhanced the SPS gene expression at the transcriptional level. Stressed cells also had higher activities of sucrose cleaving enzymes, such as alkaline invertase and sucrose synthase. The (14)C-sucrose isolated from normal and stressed cells had (14)C-fructose and (14)C-glucose ratios of 0.68 and 1, respectively. These data suggest the continual cycling of degradation and synthesis of sucrose in both types of cells. Among the enzymes used in constructing such futile cycling, besides invertase and SPS, sucrose synthase (SS) should be involved in normal cells, but not in stressed ones. It is apparent that the osmotic stress caused a significant change in the pattern of sucrose metabolism.

The genetic resource of rice plant is so rich that many high yield and disease resistant cultivars adaptable to diversified agroenvironments have been bred, and currently it is the major staple food source for one half of world population. As in other cereals, the main constituent of rice grain is starch, thus the grain filling capacity is determined mainly by the starch-synthesizing capability of endosperm. Among the three loci of starch synthesis, starch granules formed in leaf and stem are transitory in nature. The stem starch serves as a temporary storage of photosynthate from source leaf to sink seed, and sucrose is the main form of photosynthate trafficking. ADPG is the glucose carrier between sucrose and starch, and besides ADPG pyrophosphorylase, an endosperm-specific sucrose synthase isoenzyme is another agent of ADPG synthesis. A futile cycling of sucrose synthesis-degradation is probably the mean of fine-tuning sucrose concentration to regulate metabolic activities. In the growing rice seed, the concerted functioning of multiple forms of granule bound and soluble starch synthases, branching and debranching enzymes, together with the ADPG supplying strength, determine the overall grain-filling capacity. The biochemistry, molecular biology, cell biology and molecular genetics relevant to the functioning of enzymes needed for transforming sucrose into various forms of starch were discussed.

9 Three-letter symbol Sus seems most appropriate as the mnemonic for genes encoding sucrose synthase. 9 Maize will be the type species. One of the maize genes already carries the designation Sus, so it will be named Susl. The gene in maize originally defined phenotypical ly as shrunken 1 or Sh I will be given a second designation of Sus2. 9 When report ing on the Sus2 (Shl) in maize, it would be most appropriate to use both terms. In other plants, the term Sus2 alone should be used. 9 A third gene, to be named Sus3, has been isolated from rice (Su, unpublished). 9 There are additional genes which may depart from Susl, Sus2, or Sus3. These could be tentatively designated SusO.

By controlling the concentrations of kinetin, auxin, and sucrose in the Murashige-Skoog medium, starch contents in callus culture induced from sweet potato tissues could be manipulated. Activity staining and Western analysis on PAGE plates and activity assays made on starch phosphorylase in the presence and absence of mercuric ions showed that beta-amylase is absent in callus cultures regardless of whether their starch content is high or low. This would imply that beta-amylase induction in sweet potato calli is not linked to the metabolic control through which the expression of storage function is associated, as proposed by Nakamura et al. [Plant Physiol., 96, 902 (1991)] for sweet potato leaf-petiole cuttings. Analyses of starch phosphorylase in crude extracts suggested the presence of a new starch phosphorylase in tuberous root and callus tissue. This phosphorylase is immunologically different from the tuberous root and leaf enzymes that we studied previously.

By sequencing cDNA clones, we have concluded that three distinct sucrose genes are expressed in rice (Oryza sativa cv. Tainong 67). When the amino acid sequences deduced from these cDNAs as well as those of known sucrose synthase are compared, the highest divergence is found in the C-termini. The most suitable DNA sequences for use as specific for the mRNA derived from these genes have been suggested.

ABSTRACTConcentrated fresh juice of bamboo shoots was filtered through a Sephadex G‐75 column under aseptic and anaerobic conditions. The detinning activity in the filtrate was assayed by an oxygen monitor in the presence of tin powder. A large amount of peptides with molecular weights about 1300, some nucleotides and p‐hydroxybenzaldehyde were identified as the detinning substances. Twenty peptides were isolated by means of cation and anion exchange chromatography. The primary structures of these peptides were elucidated by the subtractive Edman degradation, in which a high performance liquid chromatograph was used for amino acid and sugar analysis.

ABSTRACTA novel papain‐catalyzed acylation between N‐acetyl‐L‐homocysteine thiolactone (AHTL) and terminal or side‐chain amino groups of soy protein resulted in covalent introduction of new sulfhydryl groups and the improvement of protein functionalities. Acylation was carried out with 10% soy protein, 1% AHTL and 0.1% papain (w/v) in the presence of L‐cysteine and EDTA as activators for papain, and incubated at pH 10.0 and 20°C for 8 hr. It was proposed that acylation was a two‐step process, involving fast transthioesterification to form an acyl thioenzyme, and a subsequent aminolysis step between the acyl thioenzyme and the amino groups of protein yielding peptide or isopeptide linkages. Solubility, emulsifiability, foamability and some Theological properties of the modified soy protein increased with increase in degree of acylation. Only foam stability decreased.

ABSTRACTA method of chemical phosphorylation was developed to modify soy protein so as to improve its functional properties. The reaction was carried out by incubating soy protein isolate and cyclic sodium trimetaphosphate in an aqueous solution at pH 11.5 and 35°C for about 3 hours. The reactions ensued were the phosphoesterification of serine residues and the phosphoramidation of lysine residues in soy protein. The phosphorylated soy protein isolate prepared there‐from exhibited much improved functional properties in terms of aqueous solubility, water‐holding capacity, emulsifiability and whippability. The nutritive bioavailability of soy protein isolate was not impaired by phosphorylation.

Particulate preparations from higher plants incorporate galacturonic acid from UDP-galacturonate into a “pectin-like” material. The enzymatic reaction is fairly specific for UDP-GalUA although some incorporation of TDP-GalUA was observed with tomato particles, and a slight incorporation of CDP-GalUA with mung bean particles. The radioactive product formed from UDP-GalUA liberated GalUA, DiGalUA, and TriGalUA when treated with pectinase, indicating that it was polygalacturonic acid. More extensive studies on the nature of the product are being communicated elsewhere (Villemez, etal., 1965).

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTA New Adenylate Deaminase from Red Marine Alga Porphyra crispata*Jong-Ching Su, Chien-Chung Li, and Catherine Chongling TingCite this: Biochemistry 1966, 5, 2, 536–543Publication Date (Print):February 1, 1966Publication History Published online1 May 2002Published inissue 1 February 1966https://pubs.acs.org/doi/10.1021/bi00866a020https://doi.org/10.1021/bi00866a020research-articleACS PublicationsRequest reuse permissionsArticle Views50Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCarbohydrates and Nucleotides in the Red Alga Porphyra perforata.* I. Isolation and Identification of CarbohydratesJong-Ching Su and W. Z. HassidCite this: Biochemistry 1962, 1, 3, 468–474Publication Date (Print):May 25, 1962Publication History Published online1 May 2002Published inissue 25 May 1962https://doi.org/10.1021/bi00909a016Request reuse permissionsArticle Views264Altmetric-Citations60LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (845 KB) Get e-Alertsclose Get e-Alerts

AbstractExistence of floridoside (α‐D‐galactosylglycerol) in a purified 80% alcohol extract of Porphyra crispata was confirmed. From the hot water extract of the residue of alcohol extraction, polysaccharide was precipitated with alkali and alcohol. The polysaccharide was found to be consisted chiefly of DL‐galactose and an unidentified ketose.