Coenzymes participate in many of the enzyme analyses performed in the clinical laboratory. Supplementation of assay systems with optimal levels of coenzymes has recently been recommended as part of efforts to achieve interlaboratory standardization of enzyme measurements. Aspartate aminotransferase and alanine aminotransferase require pyridoxal phosphate for expression of enzyme activity. The r...

The gene specifying plastid transketolase (TK) of maize (Zea mays) was cloned from a cDNA library by southern blotting using a heterologous probe from sorghum (Sorghum bicolor). A recombinant fusion protein comprising thioredoxin of Escherichia coli and mature TK of maize was expressed at a high level in E. coli and cleaved with thrombin, affording plastid TK. The protein in complex with thiami...

Metabolic pathways by which ribose may be formed have been studied in this laboratory (1, 2). There is now ample proof of the existence in many organisms of enzyme systems able to form ribose-5-phosphate from glucose-6-phosphate with intermediate stages of 6-phosphogluconate and ribulose-5-phosphate. Recent studies on the metabolism of ribulose-5phosphate have shown that it may be split by a tr...

Human erythrocyte transketolase (sedoheptulose-7-phosphate: D-glyceraldehyde-3-phosphate, glycolaldehyde transferase, E.C. 2.2.1.1.) has been isolated from erythrocytes with a specific activity of 59.84 U/mg. SDS-PAGE and SE-HPLC were used both as a measure of purity and as a preparative mean to obtain a higher degree of purity. Four protein bands corresponding to molecular weights of 32,0...

Transketolase from the leaves of Nicotiana tabacum var. John William's Broadleaf is inhibited by exposure to low intensity blue light in the presence of low concentrations of FMN, which functions as a sensitizer. The degree of photoinactivation is reduced in the presence of quenchers of triplet FMN. Photoinactivation does not occur in the absence of oxygen and is also lessened in the presence o...

The blast fungus Magnaporthe oryzae threatens global food security through the widespread destruction of cultivated rice. Foliar infection requires a specialized cell called an appressorium that generates turgor to force a thin penetration hypha through the rice cuticle and into the underlying epidermal cells, where the fungus grows for the first days of infection as a symptomless biotroph. Und...

We have previously used targeted active-site saturation mutagenesis to identify a number of transketolase single mutants that improved activity towards either glycolaldehyde (GA), or the non-natural substrate propionaldehyde (PA). Here, all attempts to recombine the singles into double mutants led to unexpected losses of specific activity towards both substrates. A typical trade-off occurred be...

Metabolic pathways by which ribose may be formed have been studied in this laboratory (1, 2). There is now ample proof of the existence in many organisms of enzyme systems able to form ribose-5-phosphate from glucose-6-phosphate with intermediate stages of 6-phosphogluconate and ribulose-5-phosphate. Recent studies on the metabolism of ribulose-5phosphate have shown that it may be split by a tr...