Chitin synthetase mutants of Phycomyces blakesleeanus

Cubero, Beatriz; Ruíz-Herrera, José; Cerdá‐Olmedo, Enrique

doi:10.1007/bf00276877

Cited by 8 publications

(5 citation statements)

References 28 publications

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“…The same holds for the recent suggestion [26] that the CS inhibitory action of the nucleoside-peptides nikkomycins (for structural formulae, see [27]) results from a competition of these compounds with UDPGlcNAc or GlcNAc at the effector-binding site.…”

Section: Discussionsupporting

confidence: 73%

“…In the absence of any evidence for more than one type of allosteric site of CS, it must be discounted that GlcNAc would be a poor substitute at an effector site for UDPGlcNAc [5,101. The same holds for the recent suggestion [26] that the CS inhibitory action of the nucleoside-peptides nikkomycins (for structural formulae, see [27]) results from a competition of these compounds with UDPGlcNAc or GlcNAc at the effector-binding site.…”

Section: Compoundsupporting

confidence: 73%

See 1 more Smart Citation

Stereochemical Requirements of Chitin Synthase for Ligand Binding at the Allosteric Site for N‐Acetylglucosamine

Horsch

Mayer

Rast

1996

European Journal of Biochemistry

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The substrate kinetics of chitin synthase (CS) were non-Michaelian, irrespective of the type of enzyme preparation studied ( 1 0 5 s chitosomal CS, and 16-S CS ex walls), even in the presence of saturating GlcNAc. An unexplained idiosyncrasy of this enzyme, which is likely to be responsible for this phenomenon, is evident from the striking non-linearity of product deposition with time at low substrate or low enzyme concentrations, particularly in the absence of GlcNAc. The possibility can be excluded that this non-linearity is due to the formation of soluble by-products or intermediates in the form of chito-oligomers, as shown by HPLC/pulsed amperometric detection analysis. Additional evidence was sought for the tenet that CS is homotropicall y-heterotropically regulated, at least under steady-state reaction conditions. Substrate kinetic curves established from rate data for the linear reaction phase only were used for modelling. These could be reasonably well parameterised on the basis of the Monod mathematical model for co-operative ligand binding. Within a series of test compounds used to assess the stereochemical conditions of the allosteric site of CS for effector binding, N-acetylglucosaminono-I ,5-lactone oxime excelled. Requirements for effector binding are as follows: (a) an aminoglucopyranose skeleton with the amino function acetylated, and (b) a single-bonded 0x0-function present at C(1), which is preferentially a hydrogen bond donor, that may be equatorially spaced off, but must not be a-anomeric. The implications of these findings for chitin synthesis in vivo are discussed in terms of a mechanistically based fitness of CS to operate efficiently under vastly different combinations of substrate and effector concentrations as well as with respect to the conditions under which chitin synthase could be coordinately linked to the catabolism of chitin.

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Section: Discussionsupporting

confidence: 73%

Section: Compoundsupporting

confidence: 73%

Stereochemical Requirements of Chitin Synthase for Ligand Binding at the Allosteric Site for N‐Acetylglucosamine

Horsch

Mayer

Rast

1996

European Journal of Biochemistry

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“…If remodeling enzymes and/or proteins are responsible for cell wall loosening, it can be predicted from the results presented in this study that (a) there are fewer remodeling enzymes-proteins and/or (b) the activity of these cell wall remodeling enzymes-proteins is reduced in the stiff mutants. There is evidence that chitin synthases are involved in cell wall remodeling activity in P. blakesleeanus (Atsushi, Momany, Szaniszlo, Jayaram, & Tamotsu, 1993;Cubero, Ruiz-Herrera, & Cerdá-Olmedo, 1993;Jan, 1974). Jan (1974) demonstrated that chitin synthase activity in P. blakesleeanus sporangiophores was higher in the growing region (region where elongation takes place) compared to the non-growing region.…”

Section: Discussionmentioning

confidence: 99%

Dimensionless numbers to study cell wall deformation of stiff mutants of Phycomyces blakesleeanus

Munoz

Ortega

2019

Plant Direct

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The sporangiophores of Phycomyces blakesleeanus are large cylindrical aerial cells that elongate vertically at rates between 10 μm/min and 60 μm/min. Wild‐type sporangiophores grow toward light, opposed to gravitational acceleration and away from solid barriers (tropic responses). Sporangiophores of stiff mutants C149 and C216 exhibit diminished tropic (bending) responses. Originally, it was thought that the altered genes affect the “stiffness” (elastic wall deformation) of the cell wall. Subsequent investigations employing the pressure probe demonstrated that the irreversible (plastic) wall deformation was smaller for the stiff mutants compared to wild type and could account for the diminished tropic responses. However, it was not shown whether the elastic wall deformation was altered in these stiff mutants. Recent theoretical studies have identified dimensionless numbers that can be used to quantitate the magnitudes of biophysical processes involved in expansive growth of walled cells. In this study, dimensionless numbers are used to determine the magnitudes of elastic deformation rate, plastic deformation rate, and stress relaxation rate of the cell wall during expansive growth of the stiff mutant sporangiophores. It is found that the altered genes reduce stress relaxation rates and plastic deformation rates of the wall, but do not significantly alter the magnitude of the elastic deformation rates of the wall. These results indicate that the mutant genes reduce wall loosening chemistry in these sporangiophores and the genetic mutation is not expressed in a change in “wall stiffness,” but in “wall viscosity” or “wall extensibility.”

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“…Therefore, the substrate spectra of the two permeases partially overlap with tripeptides being transported by both (Milewski et al, 1988). Several mechanisms of resistance to nikkomycin may exist in fungi: (i) alterations in cell permeability; Yadan et al (1984) suggested that alterations in cell permeability which rendered cells unable to transport the antibiotic due to impaired dipeptide uptake were responsible for resistance observed in Nik r mutants of Candida albicans; (ii) over expression of chitin synthase activity, i.e., an amplification strategy (Ramirez-Ramirez et al, 1993); (iii) detoxification of the antibiotic (Ramirez-Ramirez et al, 1993); and (iv) alterations in the chitin synthase enzyme itself (Cubero et al, 1993). Results presented here suggest that variations in sensitivity to nikkomycin among the four species examined were due to variations in the ability of the organisms to transport the antibiotic via their peptide transport systems.…”

Section: Figmentioning

confidence: 98%

“…While there have been several investigations of the uptake of nikkomycin Z by Candida albicans (Yadan et al, 1984;Milewski et al, 1988;Payne et al, 1991;Basrai et al, 1992) and the isolation of mutant strains of C. albicans (McCarthy et al, 1985), Phycomyces blakesleeanus (Cubero et al, 1993) and Mucor rouxii (Ramirez-Ramirez et al, 1993) resistant to nikkomycin Z, there have been few studies of naturally occurring variations in sensitivity and tolerance to nikkomycin Z among different genera and species of intact fungi in culture (Gooday, 1990). These few studies have concentrated on effects of the antibiotic on Mucor rouxii (Müller et al, 1981;Furter and Rast, 1985;Zhu and Gooday, 1992) and Botrytis cinerea (Zhu and Gooday, 1992).…”

mentioning

confidence: 99%