Mung bean enzymes from

Hassid and coworkers293 reported that this mung-bean enzyme-system catalyzes the incorporation of D-glucose from GDP-D-glucose into a polysaccharide having the characteristics of cellulose and that, in the presence of GDP-D-mannose, this incorporation was stimulated. The same enzyme-system, when provided with GDP-D-mannose as the sole substrate, catalyzed the incorporation of GDP-D-mannose into a glucoman-... 

On the other hand, when GDP-D-glucose was used as the substrate, both the particulate and the digitonin-solubilized enzyme systems from mung beans and from Lupinus albus yielded only (1 — 4)-/3-D-gIucan (cellulose), practically all insoluble. 

Metal requirements for the plant enzyme closely resemble those of the microbial enzyme which require a divalent cation such as Mn for full activity. Thus, Mn " and Co activated the synthase from pea seedlings and cauliflower florets (Rothe et al., 1976 Huisman and Kosuge, 1974) but Mg " " was the most effective activator for the mung bean enzyme (Minamikawa, 1967 Minamikawa and Uritani, 1967). Three multiple forms of the enzyme were detected in pea seedlings but little is known about their intracellular... 

Fig. 6. Immunoprecipitation of wound- and auxin-induced ACC synthases from winter squash and tomato. Enzyme preparations were mixed with an antibody against winter squash wound-induced ACC synthase open symbol) or non-immune serum closed symbol), and the antigen-antibody complex was precipitated by protein A-Sepharose. ACC synthase activity remaining in the supernatant was assayed. Panel 1 the mesocarp wound-induced enzyme A, a), and the hypocotyl lAA-induced enzyme D/d)ol winter squash. The wound- and lAA-induced enzymes were mixed in 2 1 B, b) and 1 2 (C, c) activity ratios. A-D, treated with the antibody a-d, with non-immune serum. Panel 2 The wound-induced enzyme of tomato pericarp panel 3 the wound-induced enzyme of winter squash hypocotyls panel 4 the lAA-induced enzyme of winter squash hypocotyls panel 5 the lAA-induced enzyme of tomato hypocotyls and panel 6 the lAA-induced enzyme of mung bean hypocotyls [From 10]...

Altogether, these data indicate that the conditions for in vitro synthesis of cellulose must be optimized for each plant species and that there is no general recipe that can be applied regardless of the source of enzyme and conditions of extraction from the plasma membrane. So far, the only factor that is common to the protocols that have led to the highest in vitro synthesis of cellulose is the use of Mops buffer. In particular, in studies on the blackberry (Lai Kee Him et al. 2002), cotton fiber (Kudlicka et al. 1996 Peng et al. 2002) and mung bean enzymes (Kudlicka et al. 1996), as well as in our recent work on hybrid aspen (Colombani et al. 2004), Mops has been described as the buffer of choice over the previously used Tris to improve the yields of in vitro cellulose. The conditions that have led to successful in vitro syntheses of cellulose are summarized in Table 8-1. 

This section describes two representative single-strand-specific endonucleases nuclease SI from a fungus Aspergillus oryzae and mung bean nuclease from mung bean sprouts. The two enzymes are very similar in many respects both are thermostable, zinc-dependent glycoproteins of similar size and they share most of the substrate specificities. The most pronounced difference that exists between... 

Conversion of the a-D-glucopyranosyl derivative (94a) into the a-D-galactopyranosyl ester (95a) was demonstrated370 in 1951 as the first example of an enzymic reaction of a sugar nucleotide. The enzyme that catalyzes this reaction, namely, uridine 5 -(a-D-glu-copyranosyl pyrophosphate) 4"-epimerase,371 is common in Nature. Purified preparations have been obtained from yeast,372 373 Escherichia coli 374-376 mung-bean seedlings,377 wheat germ,378 and animal tissues.244,379 380... 

The effect, on substrate properties, of structural changes in the nucleoside residue, as studied with uridine 5 -(a-D-glucopyranosyl pyrophosphate) 4"-epimerases from liver339,364,394 and mung bean,364,377 is qualitatively similar to that just discussed for uridine 5 -(a-D-glu-copyranosyl pyrophosphate) dehydrogenase. The enzymes tolerate various substitutions at C-6 and C-5 (such as those resulting in derivatives of 5,6-dihydrouridine, 6-azauridine, and 5-methyluridine)... 

The hydroxyl group at C-2 of the nucleoside seems not to be significant for interaction of uridine 5 -(a-D-glucopyranosyl pyrophosphate) with liver and mung-bean epimerases, as 2 -deoxyuridine339,394 and thymidine364 derivatives are efficient substrates for these enzymes, although they are not substrates for yeast epimerase.390 The epimerase from E. coli reacts with the thymidine pyrophosphate derivative.2978... 

It has also been shown that mung beans, peas, and other plants contain a pyrophosphorylase which forms GDP-D-glucose from a-D-glucose 1-P and GTP. Based on the data obtained with enzymic plant preparations, we proposed the following mechanism for cellulose synthesis ... 

Walters and Loring (88) have purified a 3 -nucleotidase about 50-fold from mung bean sprouts (Phaseolus aureus Roxb.). The enzyme hydrolyzes 3 -AMP, 3 -GMP, 3 -CMP in decreasing order and also hydrolyzes the 3 -phosphate group of coenzyme A. (89), but it has no significant activity for 2 - or 5 -ribonucleotides. For 3 -GMP, 3 -AMP, 3 -UMP, and 3 -CMP, Km values are 0.67, 1.1, 7.7, and 15 mM, respectively. The enzyme preparation also contained acid stable ribonuclease activity (89). Both 3 -nucleotidase and acid ribonuclease were inactivated reversibly at pH 5.0 and by dialysis and this inactivation could be prevented by Zn2+. The two activities were similarly inactivated by heat at pH 5 and 7.5. Such data indicate that the two are metalloproteins— probably zinc metalloproteins. These similarities and other kinetic data provide evidence that the 3 -nucleotidase and ribonuclease activities reside in the same protein. 

An enzyme similar to the 3 -nucleotidase of mung bean has been isolated from germinating wheat seedlings and purified 800-fold (90). The preparation possessed DNase, RNase, and 3 -nucleotidase activities. These three activities were similar in pH optima, requirements for Zn2+ and sulfhydryl compounds, stability to storage, temperature inactivation... 

The conversion of D-mannose 6-phosphate into D-mannosyl phosphate is catalyzed by phosphomannomutase, an enzyme distinct from phosphoglucomutase. Both enzymes have been detected by Mathe-son705 in cassia seeds, mung beans, orchid tubers, and pea seedlings. These enzymes from cassia seeds have been separated from one another by chromatography on DEAE- and O-phosphono-cellulose columns, and further characterized. Phosphomannomutase from animal sources requires the presence of either D-galactose 1,6-bisphosphate or D-mannose 1,6-bisphosphate for activity.708 D-Mannosyl phosphate may then be enzymically transformed into GDP-D-mannose in the... 

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