Ascorbate oxidase, a copper-rich enzyme pivotal in plant metabolism, catalyzes the transformation of ascorbic acid and influences aging processes. Its activity is integral to the metabolic pathways within plants, facilitating the conversion of ascorbic acid to dehydroascorbic acid. This enzyme's function is not only crucial for the redox balance but also for the overall health and growth of plants. However, its activity can be influenced by various factors, including temperature, pH levels, environmental conditions, and plant growth regulators. Understanding these factors is essential for optimizing plant health and productivity.
Temperature plays a significant role in the activity of ascorbate oxidase. Research indicates that the enzyme exhibits dual activity peaks at temperatures below 45°C, while only one peak is observed above 50°C. The enzyme maintains its activity for up to 40 minutes when kept below 50°C. However, as temperatures rise, the peak of activity occurs earlier, and at temperatures above 55°C, the enzyme's active period dramatically shortens to just 20 minutes at 60°C.
The pH level is another critical factor that affects ascorbate oxidase. The enzyme shows heightened activity within a pH range of 5-7, with the highest activity at pH 5, reaching 1.06 activity units. As the pH value increases, the enzyme's activity diminishes, with a more pronounced decrease at higher pH levels. At pH 9, the activity drops to just 0.35 active units, indicating that the optimal pH for ascorbate oxidase is around 5.
Environmental factors such as low temperature, ozone exposure, and decompression also influence ascorbate oxidase activity. Low temperatures can preserve enzyme activity and reduce the respiration rate in fruits. Ozone has been shown to inhibit ascorbate oxidase, with a direct correlation between increased ozone concentration (up to 500 mg/m³) and stronger inhibition. This effect also helps maintain ascorbic acid content. Decompression significantly hinders enzyme activity, which can be beneficial for maintaining fruit firmness and ascorbic acid levels. The mechanism behind this may involve enzyme swelling, which interferes with substrate binding. Studies on winter jujube storage have demonstrated that wet and cold storage can suppress vitamin C degradation and ascorbate oxidase activity, enhancing the fruit's storage quality.
Plant growth regulators such as Uniconazole (S3307), Gibberellin (GA3), Abscisic acid (ABA), and 2,4-Dichlorophenoxyacetic acid (2,4-D) also affect ascorbate oxidase. S3307 and ABA treatments have been found to increase the enzyme's activity, while GA3 appears to delay this increase. The role of ABA in promoting fruit senescence may also be reflected in its impact on enzyme activity. Conversely, 2,4-D can enhance ascorbate oxidase activity at low concentrations but may inhibit it at higher levels, potentially disrupting energy metabolism and normal plant processes, leading to plant deterioration or death at toxic concentrations.
Understanding these factors is crucial for agricultural practices and the food industry, where enzyme activity can affect crop quality and shelf life. By manipulating these variables, it may be possible to enhance the nutritional value and longevity of plant-based foods.
The Naming and Characteristics of Restriction Endonucleases
Restriction enzymes, also known as restriction endonucleases, are enzymes that cut double-stranded DNA. Its cutting method is to cut the bond between the carbohydrate molecule and the phosphoric acid, and then create a nick on each of the two DNA strands without damaging the nucleotides and bases.
Introduction to Classification and Application of Cellulase
The optimum pH of cellulase is generally 4.5 to 6.5, which acts on cellulose and products derived from cellulose. Microbial cellulase is of great significance in converting insoluble cellulose into glucose and destroying cell walls in fruit and vegetable juice to improve the yield of juice.
Which Enzyme Preparations Are Often Used in Fruit and Vegetable Processing?
The so-called fruit and vegetable processing means to maximize the nutrient content of the fruit and vegetable through various processing methods, improve the edible value, and make the color, aroma and taste of the processed product more perfect.
