Synthetases sucrose synthetase

SELENOPHOSPHATE SYNTHETASE STARCH PHOSPHORYLASE SUCCINYL-CoA SYNTHETASE SUCROSE PHOSPHORYLASE TUBULIN.TYROSINE LIGASE ORTHOPHOSPHATE CONTINUOUS ASSAY Orthovanadate,... 

More-detailed studies of enzyme specificity towards the structure of the nucleoside residue have been performed with the sucrose synthetase of pea seedlings,339,384,501,502 and with wheat-germ arbutin synthetase.339,364,503 Neither enzyme can use the cytidine,504 isocyti-dine, or N3-methyluridine derivatives as substrates. On the other hand, the a-D-glucopyranosyl pyrophosphate esters of 4-thiouri-... 

Sucrose synthetase from pea seedlings seems to be more specific than similar enzymes from other plants. Unlike them, it cannot accept thymidine 5 -(a-D-glucopyranosyl pyrophosphate) as a substrate.364... 

Stoichiometric quantities of uridine diphosphate glucose were used, in the presence of a transfer enzyme, sucrose synthetase, in the soluble state (extraction given). Coupling with modified D-fructose gave sucroses modified on the D-fructosyl group, on the 1 -3-mmol scale. Thus were prepared l -deoxy-l -fluoro- (59%),98 4 -deoxy-4 -fluoro- (16%), and l -azido-l -deoxy-sucrose (15%).71 6-Deoxy-6-fluoro-D-glucose was isomerized to 6-deoxy-6-fluoro-D-fructose with isomerase, and gave 6 -deoxy-6 -fluoro-sucrose.71... 

Besides the abundant nodulins like Lb, GS, uricase and sucrose synthetase, many other enzymes involved in nodule metabolism are induced during the course of nodule development (see Verma Nadler, 1984). However, owing to the relatively low abundance of these enzymes and their mRNAs in nodules, none of the cognate genes have been cloned and new cloning strategies need to be employed to isolate these relatively less abundantly expressed nodulin sequences. 

Nuclear runoff experiments show that there is transcriptional control of ANP synthesis (at least for Adhl and Adh2, and sucrose synthetase ... 

Pontis, H.G. and Wolosiuk, R.A., Sucrose synthetase. I. Effect of trypsin on the cleavage activity, FEBS Lett., 28, 86-88, 1972. 

Pontis, H.G., Wolosiuk, R.A., Fernandez, L.M., and Bettinelli, B., Role of sucrose and sucrose synthetase in Helianthus tuberosus, in Biochemistry of the Glycosidic Linkage, Academic Press, New York, 1972, pp. 239-265. 

Sakalo, V.D. and Lukashova, R.G., Activity and immunochemical comparison of sucrose synthetase from plant storage organs, Fiziologiya Rastenii, 40, 265-270, 1993. 

Salerno, G.L., Gamundi, S.S., and Pontis, H.G., A procedure for the assay of sucrose synthetase and sucrose phosphate synthetase in plant homogenates, Anal. Biochem., 93, 196-199, 1979. 

Wolosiuk, R.A. and Pontis, H.G., Sucrose synthetase. II. Kinetic mechanism, Arch. Biochem. Biophys., 165, 140-145, 1974. 

Fig. 6.—Hypothetical Model for the Biosynthesis of Cellulose.184 [Numbers refer to reactions catalyzed by the following enzymes 1, invertase (EC 3.2.1.26) 2, sucrose synthetase 3, hexokinase (EC 2.7.1.1) 4, phosphoglucomutase (EC 2.7.5.1) 5, UDP-glucose pyrophosphorylase and 6, 7, and 8, hypothetical reactions in the pathway to cellulose.]...

DAHP synthetase, 251, 255 Dehydroquinase, 258 Dehydroshikimate riductase, 259 Dextrans, 341 acid hydrolysis of, 349 chain lengths of, 345, 346 cuprammonium complexes of, 355 electron microscope studies on, 349 enzymic synthesis of, 342, 345, 355 from sucrose, 342 flow birefringence studies on, 349 fructose-containing, 359 infrared absorption spectra of, 352 isolation of, 343... 

Sucrose Phosphate Synthetase (Salvuccl and Cratts-Brandner, 1991)... 

Sucrose phosphate synthetase catalyzes the reaction of UDP-glucose with fructose-6-P to form sucrose-6-P and UDP. This step is the penultimate step in the synthesis of sucrose in leaves. The chromatographic method can be applied to many UDP-glucose-requiring enzymes. The method eliminates the need for treatment of reaction mixtures with alkaline phosphatase. 

Although the bundle sheath chloroplasts contain all the enzymes of the RPP cycle, there is now evidence that some of the 3-PGA formed by the activity of rubisco is exported to the mesophyll cells [9]. Bundle sheath chloroplasts of maize are deficient in photosystem II activity and apparently cannot produce sufficient NADPH to reduce all of the 3-PGA formed to triose phosphate. Responsibility for this step is thus shared with the mesophyll chloroplasts which recycle triose phosphate to the bundle sheath as DHAP. This transport of 3-PGA from bundle sheath to mesophyll permits the synthesis of sucrose in the mesophyll cell cytoplasm. The evidence suggests that the mesophyll cells are the major site of sucrose synthesis [10-13]. Sucrose phosphate synthetase, one of the regulatory enzymes of sucrose synthesis and fructose 6-phosphate, 2-kinase (Fru-6-P,2K), the enzyme synthesizing fructose 2,6-bisphosphate — a potent regulator of cytoplasmic sucrose synthesis (see Section 5.4.1) — are both almost completely confined to the mesophyll cells. 

MSAS from P. patulum was separated from the FAS via sucrose gradient centrifugation [121,122] and thus shown to constitute a distinct multifunctional enzymatic system. It was purified to homogeneity and found to be a 190 kDa multifunctional enzyme [22,120]. The enzyme was more stable in the presence of its substrates and at mildly basic pH values. The pH optimum of the enzyme was 7.6 and apparent K values for its substrates were 10 pM (acetyl-CoA), 7 pM (malonyl CoA), and 12 pM (NADPH) [115,120,123]. The rate for triacetate lactone formation in the absence of NADPH was determined to be ten-fold lower than for 6-MSA formation (Fig. 5) [120]. Analogous to FASs and peptide synthetases, 4 -phosphopantetheine is a covalently bound cofactor of 6-MSAS [124]. Likewise, iodoacetamide and N-ethylmaleimide were found to inactivate the enzyme, suggesting the presence of catalytic sulfhydryl residues in 6-MSAS [124]. Furthermore, in the presence of malonyl CoA and NADPH, low concentrations of iodoacetamide convert 6-MSAS into a malonyl CoA decarboxylase. Without external addition of acetyl-CoA, 6-MSAS decarboxylates the malonyl group and the derived acetyl moiety is used as a starter unit for the formation of 6-MSA [125]. 

Sucrose synthetase. The fructose derivatives 1-azido-l-deoxy-, 1-fluoro-l-deoxy-, 6-deoxy-, 6-fluoro-6-deoxy-, and 4-fluoro-4-deoxy-fructose have been used as glycosyl acceptors in the sucrose synthetase-catalyzed synthesis of sucrose analogs12031. 6-Deoxy- and 6-fluoro-6-deoxy-fructose were generated in situ from the corresponding glucose derivatives under catalysis by glucose isomerase[2031. Sucrose synthetase has also been extensively employed in the synthesis of nucleotide sugars[2041. 

Figure 13-9. General scheme for an enzyme-catalyzed synthesis of sucrose with UDP-glucose1821. i) sucrose synthetase ii) pyruvate kinase iii) UDP-glucose pyrophosphorylase iv) inorganic pyrophosphatase.

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