Regulatory mechanisms of β‐glucan synthases in bacteria, fungi, and plants

Abstract

Mullins, J. T. 1990. Regulatory mechanisms of ^-glucan synthases in bacteria, fungi, and plants. Plant, The evidence accumulated to date indicates that 1,3-^-glucan synthase (EC 2.3.1.12) and 1,4-^-glucan synthase (EC 2.4.1.12) are regulated by different effectors. Further that the same synthase has different effectors, depending upon its presence in green plants, fungi, and bacteria, Synthases from plants require divalent cations and /?linked glucosides, whereas fungal enzymes require neither eations nor ;3-glucosides, but most require nucleoside triphosphates for activation. Two endogenous effectors have been characterized and shown to produce activation in vitro. One is 3',5'-cyclic diguanylic acid that is the activator of cellulose synthase in bacteria. The other is â -linked glucosyl dioleoyl digiyceride from mung bean, capable of activating synthases that produce both ^-(1-3) and;5-(l-4) products. The results of product analysis of the y3-tinked glucoside activated reaction suggest that the synthesis of (1-3) and (1-4) glucosyl linkages may share a common enzyme in plants. All synthases utilize uridine 5'-diphosphoglucose (UDPG) and are associated with the plasma membrane. Efforts to solubilize the synthases from cellular fractions enriched in plasma membranes have been generally successful. The purification of the soluble enzymes, however, remains a major obstacle to the full understanding of their regulation.

Structural and mechanistic insights into fungal β-1,3-glucan synthase FKS1

“…Moreover, EDTA can support the catalytic activity of the enzyme and Mg 2+ significantly inhibited the activity (Extended Data Fig. 1m ), consistent with previous studies 25 , 29 , 30 . Introduction of a K1261A mutation, an enzyme inactivation mutation discovered from our structural analysis (see the section ‘The active site and catalytic mechanism’), to FKS1(S643P) completely inactivated the product synthesis activity of the hyperactive enzyme (Extended Data Fig.…”

Determinação da concentração de beta-glucano em cogumelo Agaricus blazei Murill por método enzimático

“…De fato, cereais contêm essencialmente β−glucanos com ligações mistas de β(1→3)(1→6), enquanto cogumelos apresentam maiores quantidades de β(1→4)(1→6) que β(1→3)(1→4) e diferentes ligações simples como β(1→3), β(1→4) e β(1→6) [23]. Na Tabela 2, são apresentados os teores de β−glucano presentes nas amostras de cogumelo A. blazei em duas condições de cultivo.…”

Cyclic diguanylic acid stimulates 1,4-μ-glucan synthase from Saprolegnia monoica

“…In order to maintain fungal growth, a coordination of the synthesis of cell-wall components must exist, and it is expected that glycosyl transferases would be subject to strict regulation. Using cell-free extracts, several factors have been identified as potential regulators of these enzymes [4]. 1,3-/3glucan synthases from Ascomycetes and Basidiomycetes are stimulated by nucleoside triphosphates (ATP, GTP), but the transfer of the terminal phosphate is not required for the activation step [5,6].…”