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F Fang

Publications and source records attributed to F Fang.

136 records · Page 8Linked to original sources
PubMed1977

5-O-beta-D-Galactofuranosyl-containing exocellular glycopeptide of Penicillium charlesii. Incorporation of mannose from GPD-D-mannose into glycopeptide.

Three-day-old Penicillium charlesii mycelia were broken with Al2O3 in a buffered system and the membranes were separated on a linear gradient of sucrose concentrations. The most active guanosine 5'-(alpha-D-mannopyranosyl pyrophosphate):glycopeptide mannopyranosyltransferase (GPD-D-mannose mannosyltransferase) was found in two unresolved membrane fractions ( p congruent to 1.1 g/cm3). This preparation incorporated [14C]mannose from GDP-D-[14C]mannose both into endogenous acceptors and added peptidophosphogalactomannan. Mannosyltransferase activity is optimum at pH 7.0 in 0.05 M Tris/maleate buffer, and 17 mM Mn2+. Replacement of Mn2+ with Fe2+, Mg2, Co2+, Ca2+ or Ni2+ greatly reduced the mannosyltransferase activity. [14C]Mannose incorporation from GDP-D-[14C]mannose into acceptors is linearly dependent on enzyme concentration. Mannosyl incorporation into peptidophosphogalactomannan is linear for 3 h and continues for at least an additional 4 h. In contrast, the rate of mannosyl incorporation into endogenous acceptor(s) decreases after 60 min and there is no incorporation after 2 h. A series of possible acceptors related to peptidophosphogalactomannan were tested and it was found that treatment of peptidophosphogalactomannan with 0.01 N HCl at 100 degrees did not appreciably decrease the effectiveness of the acceptor even though this treatment removes the galactofuranosyl residues. In contrast, treatment of peptidophosphogalactomannan with 0.5 N NaOH rendered the products nearly incapable of accepting mannosyl residues from GDP-D-mannose. Derivation of peptidophosphogalactomannan with 2,4-dinitrobenzene also decreased its effectiveness as a mannosyl acceptor. [14C]Mannose from GDP-D-[14C]mannose was incorporated into both the oligosaccharide and phosphogalactomannan regions of peptidophosphogalactomannan. Treatment of the [14C]peptidophosphogalactomannan product, with 0.4 N NaOH released [14C]mannosyl-containing residues which eluted in the mannobiose and polysaccharide fractions from BIo-Gel P2. Approximately 90% of the 14C was in mannobiose. The [14C]mannose was shown to be transferred to the mannosyl-(seryl/threonyl) region of the acceptor. Acetolysis of [14C]peptidophosphogalactomannan resulted in the isolation of [14C]mannose, [14C]mannobiose, and [14C]polysaccharide. Small quantities of 14C were obtained in mannotriose and mannotetraose. The time course of [14C]mannose incorporation into the oligosaccharide region of peptidophosphogalactomannan showed a continual increase over a 4-h interval. In contrast, there was no major increase after 1 h in [14C]mannose incorporated into the polysaccharide region. The enzyme catalyzing incorporation of mannose into the polysaccharide region of peptidophosphogalactomannan was solubilized by treatment of the membranes with Triton X-100.

Cations, Divalent↗
PubMedDate not supplied

Estimating runoff phosphorus losses from calcareous soils in the Minnesota River basin.

Bioavailable phosphorus (BAP) in stormwater runoff is a key issue for control of eutrophication in agriculturally impacted watersheds. Laboratory experiments were conducted in soil runoff boxes to determine BAP content in simulated storm runoff in 10 (mostly) calcareous soils from the Minnesota River basin in southern Minnesota. The soluble reactive phosphorus (SRP) portion of the runoff BAP was significantly correlated with soil Mehlich-III P, Olsen P, and water-extractable P (all r2 > 0.90 and p < 0.001). A linear relationship (r2 = 0.88, p < 0.001) also was obtained between SRP in runoff and the phosphorus saturation index based on sorptivity (PSIs) calculated with sorptivity as a measure of the inherent soil P sorption capacity. Runoff levels of BAP estimated with iron oxide-impregnated paper were predicted well by various soil test P methods and the PSI, of the soils, but correlation coefficients between these variables and runoff BAP were generally lower than those for runoff SRP. Using these relationships and critical BAP levels for stream eutrophication, we found corresponding critical levels of soil Mehlich-III P and Olsen P (which should not be exceeded) to be 65 to 85 and 40 to 55 mg kg(-1), respectively.

Agriculture↗