1、Humic acid aggregates with laccase and decreases the performance of the

Laccases are among the best-rated enzymes for industrial and environmental applications, yet their use in bioremediation is limited by interference from environmental components like humic acid (HA).

2、Understanding the Role of Humic Acids on Crop Performance

Reviewed literature shows that HA can positively affect soil physical, chemical, and biological characteristics, including texture, structure, water holding capacity, cation exchange capacity, pH, soil carbon, enzymes, nitrogen cycling, and nutrient availability.

3、Influence of Soil Humic and Fulvic Acid on the Activity and Stability

Humic substances (HS), including humic acids (HA) and fulvic acids (FA), are important components of soil systems. HS form strong complexes with oppositely charged proteins, which will lead to changes in the enzyme activity.

4、Structure

In addition to its role in soil conditioning, HA is essential in mitigating plant stress. It achieves this by modulating antioxidant enzyme activity, stabilizing cellular membranes, and alleviating the adverse effects of abiotic stressors such as salinity, drought, and heavy metal toxicity.

5、Humic acids as drivers of plant growth: regulating root development and

Humic acids (HA) influence plant growth and development through various mechanisms that depend on the source and concentration of HA, as well as the specific plant organ and its developmental stage.

Humic acid regulates gene expression and activity of antioxidant

Humic acid (HA) plays an essential role in plant growth, carbon and nitrogen cycling regulation, and soil structure stability. It induces changes in plant primary and secondary metabolism associated with abiotic stress tolerance.

Advances in humic acid for promoting plant growth and its mechanism

Objectives Humic acid plays an important role in Chinese agricultural production. Many research results have showed that humic acid could prompt plant growth.

Functions of biostimulant Humic Acids

★ Humic Acids can form complexes or chelates with trace elements, adjust the ratio and balance of macroelements and trace elements, and strengthen the synthesis and operation of enzymes on sugars, starch, protein, fat and various vitamins.

Effect of Humic substances on soil properties and crop production: A

Humic acid stimulates the plant growth consequently yield by enhancing the uptake of plant nutrients and also acting on various mechanisms such as cellular respiration, photosynthesis, protein synthesis and enzyme activities.

Humic substances: Structure, function and benefits for

This review offers an insight into the various structural and functional aspects of HSs, particularly fulvic acid and humic acid. The dynamic and interactive nature of HSs creates a framework for sustainable agriculture.

Humic acid synthesis enzyme (HASE) is a critical enzyme involved in the biosynthesis of humus, primarily responsible for converting organic matter into humic acid. Humic acid, a complex organic compound rich in carbon, nitrogen, sulfur, and other elements, is widely distributed in soil, water, and the atmosphere, playing significant ecological roles in environmental systems.

1. Definition and Structure

Humic acid synthesis enzyme is a protein belonging to the class of peptide enzymes. It consists of two subunits, each containing multiple amino acid residues. These residues are linked by covalent bonds to form a complete protein molecule. The structure of HASE determines its catalytic function and active site configuration.

2. Catalytic Mechanism

The catalytic mechanism of HASE involves multiple steps, including substrate activation, enzyme-catalyzed reactions, and product release. During substrate activation, HASE first recognizes and binds to the substrate molecules. In the enzyme-catalyzed reaction stage, specific functional groups in the substrate are transformed into humic acid. Finally, during product release, the substrate is decomposed into small molecules such as amino acids and fatty acids, which can further participate in humus biosynthesis.

3. Substrate Activation

HASE must first recognize and bind to substrate molecules via a substrate-specific recognition site located in its active center. This site contains specific amino acid residues that interact with the substrate, activating its functional groups and initiating the enzymatic reaction.

4. Enzyme-Catalyzed Reaction

This is the core functional stage of HASE, involving conformational changes in the active center to form a catalytic site. The reaction proceeds as follows:

• a. Substrate-enzyme interaction: Substrate molecules enter the active center and interact with amino acid residues.
• b. Substrate activation: Functional groups in the substrate (e.g., amino acids) undergo oxidation or reduction to form carboxyl or amino groups, promoting humic acid formation.
• c. Catalytic progression: Conformational changes in the active center enhance catalytic efficiency, accelerating humic acid synthesis.
• d. Product release: Decomposed substrates become small molecules, which may polymerize or cross-link to form humus.

5. Influencing Factors

The activity of HASE is affected by:

• a. Substrate concentration: Higher concentrations increase activity but excessive levels may inhibit efficiency.
• b. Temperature: Elevated temperatures boost activity up to an optimal point, beyond which enzyme denaturation occurs.
• c. pH: Lower pH values generally enhance activity, while higher pH levels reduce it.
• d. Metal ions: Certain ions (e.g., transition metals) may activate the enzyme, but excess can lead to inhibition or byproducts.

6. Application Prospectives

HASE holds promise in environmental protection and agricultural production:

• Environmental protection: Humic acid adsorbs heavy metals and pollutants, improves soil structure, and enhances fertility and water retention. Developing efficient HASE could aid ecological restoration.
• Agricultural production: Humic acid acts as a fertilizer and pesticide, improving soil health, crop yield, and stress resistance. Efficient HASE could revolutionize agricultural practices.

HASE plays a pivotal role in environmental and agricultural contexts. Deepening research on its mechanisms and regulation could provide theoretical and technical support for sustainable development in these fields.