The pseudoenzyme β-amylase9 from Arabidopsis binds to and enhances the activity of α-amylase3: A possible mechanism to promote stress-induced starch degradation.

Starch accumulation in plant tissues provides an important carbon source at night and for regrowth after periods of dormancy and in times of stress. Both ɑ- and β-amylases (AMYs and BAMs, respectively) catalyze starch hydrolysis, but their functional roles are unclear. Moreover, the presence of catalytically inactive amylases that show starch excess phenotypes when deleted presents an interesting series of questions on how starch degradation is regulated.

gene of unknown function Gohir.A02G161000 encodes a potential transmembrane Root UVB Sensitive 4 Protein with a putative protein-protein interaction interface.

A gene of unknown function, Gohir.A02G161000.1, identified in was studied using computational sequence and structure bioinformatics tools.

gene of unknown function Gohir.A02G131900 encodes a potential plant-specific, dual-domain exo-1,3-β-glucosidase.

A gene of unknown function, Gohir.A02G131900.1, identified in was studied using computational sequence and structure bioinformatic tools.

gene of unknown function, Gohir.A02G039501.1, encodes a potential DNA-binding ALOG protein involved in gene regulation.

A protein of unknown function encoded by gene Gohir.A02G039501.1 in , was studied using sequence and structure bioinformatic tools leading to its proposed function as a nuclear, DNA-binding ALOG protein involved in gene regulation during organ boundary specification and maintenance.

gene of unknown function Gohir.A03G0737001 encodes a potential Chaperone-like Protein of protochlorophyllide oxidoreductase (CPP1).

A gene of unknown function identified in , Gohir.A03G0737001.1, was studied using sequence and bioinformatic tools.

gene of unknown function Gohir.A03G007700.1 encodes a potential VAN3-binding protein with a phosphoinositide-binding site.

A gene of unknown function, Gohir.A03G007700.1 (gene ID: Gohir.

gene of unknown function, Gohir.A02G044702.1, encodes a potential B3 Transcription Factor of the REM subfamily.

A gene of unknown function, Gohir.A02G044702.1, identified in was studied using sequence and structure bioinformatic tools.

Review: The Arabidopsis β-amylase (BAM) gene family: Diversity of form and function.

Multi-gene families present a rich research area to study how related proteins evolve to acquire new structures and functions. The β-amylase (BAM) gene family is named for catalytic members' ability to hydrolyze starch into maltose units. However, the family also contains proteins that are catalytically inactive, have additional domains, or are not localized with a starch substrate.

Quaternary Structure, Salt Sensitivity, and Allosteric Regulation of β-AMYLASE2 From .

The β-amylase family in has nine members, four of which are both plastid-localized and, based on active-site sequence conservation, potentially capable of hydrolyzing starch to maltose. We recently reported that one of these enzymes, BAM2, is catalytically active in the presence of physiological levels of KCl, exhibits sigmoidal kinetics with a Hill coefficient of over 3, is tetrameric, has a putative secondary binding site (SBS) for starch, and is highly co-expressed with other starch metabolizing enzymes. Here we generated a tetrameric homology model of Arabidopsis BAM2 that is a dimer of dimers in which the putative SBSs of two subunits form a deep groove between the subunits.

Glutathionylation Inhibits the Catalytic Activity of Arabidopsis β-Amylase3 but Not That of Paralog β-Amylase1.

β-Amylase3 (BAM3) is an enzyme that is essential for starch degradation in plant leaves and is also transcriptionally induced under cold stress. However, we recently reported that BAM3's enzymatic activity decreased in cold-stressed Arabidopsis leaves, although the activity of BAM1, a homologous leaf β-amylase, was largely unaffected. This decrease in BAM3 activity may relate to the accumulation of starch reported in cold-stressed plants.

Arabidopsis β-Amylase2 Is a K-Requiring, Catalytic Tetramer with Sigmoidal Kinetics.

The Arabidopsis () genome contains nine β-amylase () genes, some of which play important roles in starch hydrolysis. However, little is known about BAM2, a plastid-localized enzyme reported to have extremely low catalytic activity. Using conservation of intron positions, we determined that the nine Arabidopsis genes fall into two distinct subfamilies.

β-Amylase1 and β-amylase3 are plastidic starch hydrolases in Arabidopsis That Seem to Be Adapted for Different Thermal, pH, and stress conditions.

Starch degradation in chloroplasts requires β-amylase (BAM) activity, which is encoded by a multigene family. Of nine Arabidopsis (Arabidopsis thaliana) BAM genes, six encode plastidic enzymes, but only four of these are catalytically active. In vegetative plants, BAM1 acts during the day in guard cells, whereas BAM3 is the dominant activity in mesophyll cells at night.