Catalase and ascorbate peroxidase—representative H2O2-detoxifying heme enzymes in plants

Abstract

Plants have to counteract unavoidable stress-caused anomalies such as oxidative stress to sustain their lives and serve heterotrophic organisms including humans. Among major enzymatic antioxidants, catalase (CAT; EC 1.11.1.6) and ascorbate peroxidase (APX; EC 1.11.1.11) are representative heme enzymes meant for metabolizing stress-provoked reactive oxygen species (ROS; such as H2O2) and controlling their potential impacts on cellular metabolism and functions. CAT mainly occurs in peroxisomes and catalyzes the dismutation reaction without requiring any reductant; whereas, APX has a higher affinity for H2O2 and utilizes ascorbate (AsA) as specific electron donor for the reduction of H2O2 into H2O in organelles including chloroplasts, cytosol, mitochondria, and peroxisomes. Literature is extensive on the glutathione-associated H2O2-metabolizing systems in plants. However, discussion is meager or scattered in the literature available on the biochemical and genomic characterization as well as techniques for the assays of CAT and APX and their modulation in plants under abiotic stresses. This paper aims (a) to introduce oxidative stress-causative factors and highlights their relationship with abiotic stresses in plants; (b) to overview structure, occurrence, and significance of CAT and APX in plants;

Photosynthesis is differently regulated during and after copper‐induced nutritional stress in citrus trees

“…Similar to citrus trees, increased activities of SOD followed by APX in sugarcane were important to prevent damages to the photosynthetic machinery of plants under drought stress (Sales et al ). This emphasizes the importance of understanding the balance between activities of APX and CAT enzymes, and possibly other peroxidases not analyzed in this study, which generally have a different role in the elimination of H 2 O 2 (Gratão et al , Anjum et al , Hippler et al ).…”

“…Superoxide dismutase (SOD, EC 1.15.1.1) is the first enzyme that reduces the superoxide anion () to hydrogen peroxide (H 2 O 2 ). Then, the excess of H 2 O 2 in cells is eliminated by catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11) or guaiacol peroxidase (Anjum et al ).…”

Peroxisomes: versatile organelles with diverse roles in plants

“…Mutants of NCA1 display strongly reduced activities for all three Arabidopsis CATs and absence of autophagy-dependent cell death (Hackenberg et al, 2013). Peroxisomal APX amount can be induced by stress, and overexpression of peroxisomal APXs confers stronger resistance to abiotic stresses in various plant species (reviewed in Anjum et al, 2016). Peroxisomal membrane-associated APX proteins have a higher affinity for H 2 O 2 than CATs, and it has been proposed that their function is to prevent H 2 O 2 from leaking out of the peroxisome .…”

“…Arabidopsis APX3 and APX5 are both localized to peroxisomes . Peroxisomal APX amount can be induced by stress, and overexpression of peroxisomal APXs confers stronger resistance to abiotic stresses in various plant species (reviewed in Anjum et al, 2016). Knockdown of a peroxisomal APX in rice cat ameliorates the oxidative stress caused by photorespiration-derived H 2 O 2 , suggesting that APX and CAT are not redundantly involved in photorespiration, and removal of APX may trigger a mechanism which acts to compensate for the lack of CAT (Sousa et al, 2015).…”

Effects of potassium‐solubulizing and photosynthetic bacteria on tolerance to salt stress in maize

“…APX enzymatic activity was measured following the method of Nakano and Asada (1981). In chloroplasts, APX catalyses the high-efficiency removal of H 2 O 2 , oxidizing ascorbic acid in the presence of H 2 O 2 (Anjum et al 2016). The APX enzymatic activity measurement system included 1Á5 ml of PBS (pH 7Á8), 1Á2 ml of 0Á5 mmol l À1 ascorbic acid, 1Á2 ml of 0Á1 mmol l À1 H 2 O 2 and 0Á1 ml of enzyme extract.…”