---

Aims: Invertase is an enzyme that is widely used in industries. The main source of industrial production of invertase is yeast Saccharomyces cerevisiae (S. cerevisiae). Increasing thermal stability makes an important contribution to improving productivity in related production. The aim of this study was increasing thermal stability of Saccharomyces cerevisiae recombinant protein invertase by site-directed mutagenesis.
Materials and Methods: In the present experimental study, using invertase enzyme from thermophilic bacteria, Thermotoga maritima as template, it was decided to replace the threonine 345 and asparagine 349 amino acid with alanine, using site-directed mutagenesis and in Pichia pastoris, cloning was performed with the SOEing polymerase chain reaction. The activity of natural and mutant recombinant invertase enzymes at different temperatures, different pHs, stability duration, and thermal-performance stability, and Michaelis–Menten kinetics were drawn.
Findings: The thermal-structural stability of the natural and mutant invertease enzymes at 55°C showed that the mutant enzyme had a higher thermal stability at 55°C compared with the natural enzyme. Both natural and mutant enzymes exhibited a similar trend in functional stability. Reduction of K_m and increase of V_max in sucrose substrate and 5-fold increase in K_cat/K_m ratio of mutant enzyme was observed.
Conclusion: Site-directed mutagenesis has no negative effect on the amount of production as well as the secretion of recombinant protein invertase and increases enzyme activity. The mutant enzyme has a higher structural stability than the natural enzyme without altering its functional stability.

---

Effect of different CO₂ concentrations on sucrose metabolizing enzymes and on carbohydrate metabolism was studied for eight blackgram (Vigna mungo L. Hepper) genotypes grown in open top chambers under ambient (380 µmol mol^-1) vs. elevated CO₂ (550 and 700 µmol mol^-1) levels. The higher acid invertase activity over neutral invertase indicated the major role of acid invertase in sucrose breakdown. Higher acid invertase activity over Sucrose Synthase (SuSy) suggested the major role of invertase in sucrose breakdown and sucrolysis. Sucrose Phosphate Synthase (SPS) activity did not match with sucrose pool sizes in mature leaves and rather varied among genotypes. Plants exposed to higher CO₂ concentrations showed higher starch and sucrose contents as compared with those exposed to ambient CO₂. Leaf starch content being found several-folds higher than sucrose throughout the study indicated its major role in regulating assimilate partitioning. Increase in glucose vs. fructose concentrations for genotypes grown under elevated CO₂ conditions ranged from 20 to 90% and from 10 to 140%, respectively. The hexoses/sucrose ratio for elevated CO₂ concentration was approximately 0.8-1.6, however for ambient CO₂ content it approximately amounted to unity. Genotypes IC436720, IC519805, IC343952, and IC282009 with low hexose/sucrose ratio representing high CO₂ assimilation along with high sucrose formation indicated better tolerance to elevated CO₂ for carbon partitioning and carbohydrate metabolism. The up-regulation of leaf carbohydrate metabolizing enzymes of low hexose/sucrose as well as low sucrose/starch ratios for the genotype IC436720 (as compared with other genotypes) improved its photosynthetic capability which coupled with its better efficiency of carbon partitioning (indicative of better acclimation to elevated CO₂) could prove beneficial to its growth and productivity in the future change of climatic conditions.

---

Honey is a natural product that has long been used for treatment in addition to nutrition. In this regard, the antimicrobial effect of some Iranian kinds of honey against antibiotic-resistant bacterial strains and the relationship between this effect and the enzymatic activity of honey samples were evaluated. In this study, the protein content of 20 honey samples before and after extraction was determined and analyzed by SDS-PAGE technique. Then the activity of glucose oxidase, amylase, invertase, and catalase enzymes of each honey was measured. Inhibition of the tested bacterial strains in the presence of honey was investigated by ager well diffusion method and the relationship between enzymatic activity with antibacterial effect and freshness of honey was evaluated. The protein content of the samples before extraction ranged from 0.4 06 0.06 to 1.0 64 64.19 mg/g honey and after extraction this amount decreased by about 50% or less. In the protein profile of all kinds of honey after electrophoresis, 3 bands related to amylase, invertase, and glucosidase enzymes were visible. The activity of enzymes was assigned to glucose oxidase> invertase> amylase> catalase, respectively. The selected honey samples did not affect Staphylococcus epidermidis and had the least effect on Pseudomonas aeruginosa. After honey inoculation, the inhibitory pattern of Escherichia coli and Enterococcus faecalis were similar, but a different inhibitory pattern was observed from Staphylococcus aureus strain. This study showed that glucose oxidase plays an important role in bacterial inhibition, but this role fluctuates in catalase-positive strains. Also, Amylase and invertase enzymes can be a measure of the freshness of honey.

---

Developing high-yielding varieties of sunflower as oilseed staple crops requires knowledge of physiological and molecular mechanisms involved in yield formation. Source strength, sink demand, and their interactions play crucial roles in the yield formation of sunflowers. The persistence of assimilate flux to the developing grains mainly determines sink demand. There was no information on the molecular mechanism for assimilate flux to the sink organ of sunflowers. To shed light on molecular events engaging in assimilate flux to sink organs, two experiments were carried out on five sunflower inbred lines differing in their grain yields. Source-related parameters (such as leaf biomass, area, and number) and sink-associated attributes (such as floret number at the first anthesis and capitulum biomass and diameter, in addition to changes in biomass of capitulum and stem, at the first anthesis with those at physiological maturity) were evaluated across all the inbred lines. The Invertase gene expression level was measured on the receptacle base of three inbred lines, showing discrepancies in the source, sink, and grain yield performances. While no significant correlation was found between source strength and sink demand with grain yield, the results showed that higher grain yield was likely attributed to the persistence of assimilate flux to the capitulum base during grain filling. This phenomenon is discussed to be due to higher Invertase activity in the receptacle base.