A Cyanotoxin Primer for Drinking Water Professionals

Spies

et al. 2019

Journal of Toxicology

Self Cite

Permanganate pretreatment of drinking water is effective in transforming dissolved, noxious contaminants and in reducing halogenated by-products. Permanganate targets specific compounds such as taste and odor compounds, disinfection precursors, manganese, and natural organic contaminants that are not removed readily by conventional treatment alone. Cyanobacterial blooms (cHABs) can increase disinfection by-product precursors as well as the cyanotoxin, microcystin (MC), a potent liver toxin. MC toxicity is conferred by a unique, conserved amino acid, Adda, that inhibits protein phosphatase 1 and 2A. Although over 150 MC congeners have been reported, thousands of MCs are statistically possible. Over the last ten years, one congener, MC-LA, has been reported with increasing frequency, making it one of the most common cyanotoxins identified in North American freshwater systems; yet its oxidation has not been widely studied. Frequently, Adda specific enzyme-linked immunosorbent assay (ELISA) and protein phosphatase inhibition assay (PPIA) are used to quantitate total MCs to evaluate treatment efficiency and exposure. Anecdotal reports suggest that MC degradation products can cause interference with the Adda-ELISA. MC-LA was used as the model MC compound in this study. PPIA quantitation of MC-LA in water agreed with liquid chromatography high resolution mass spectrometry (LC/HRMS), whereas the ELISA quantitation did not agree with LC/HRMS quantitation. We determined the second order rate constant for MC-LA as 118 ± 9 M−1 s−1, the activation energy to be 21.2 kJ mol−1, and the rate to be independent of pH between pH 6 and 9. Ten oxidation products (OPs) were observed by LC/HRMS and three primary reaction pathways are proposed. The reaction pathways were used to explain differences in the quantification by Adda-ELISA, HRMS, and PPIA. The oxohydroxylation of MC-LA produced two major OPs, C46H67N7O14 [M+H] + = 942.4819 and C46H69N7O15 [M+H]+ =960.4925. Major OPs may contain an unmodified Adda and are the likely cause of interference with the Adda-ELISA. Several governmental agencies recommend the use of the Adda-ELISA to determine the MC quantitation for treatment efficiency and customer exposure; yet our results suggest that these or other OPs interfere with the Adda-ELISA causing artificially high values for total MCs.

Section: Introductionmentioning

confidence: 99%

Permanganate Oxidation of Microcystin-LA: Kinetics, Quantification, and Implications for Effective Drinking Water Treatment

Spies

et al. 2019

Journal of Toxicology

Self Cite

“…The investigation of these reductive dehalogenases is not only of great interest from physiological and biochemical point of view,b ut also of environmental importance.T he reason is that these enzymes are capable of degrading anthropogenic halo-genatedc ompounds, like perchloroethylene (PCE) and trichloroethylene( TCE), which are the pervasivec ontaminants in groundwaters ystems. [4,5] An umber of reductived ehalogenases have been purified and characterized, including PceA, [6][7][8] CprA, [9,10] Tc eA, [11] VcrA, [12] and NpRdhA. [13] This family of enzymes differs significantly from other knownC oe nzymes that enable diversec hemical transformations without the consumption of external electrons,s uch as methionine synthase, [14] ornithine 4,5-aminomutase, [15] ethanolamine ammonia-lyase, [16] methylmalonyl-CoA mutase, [17] lysine 5,6-aminomutase, [18] and methanol:cobalamin methyltransferase.…”

Section: Introductionmentioning

confidence: 99%

Unraveling the Mechanism and Regioselectivity of the B12‐Dependent Reductive Dehalogenase PceA

Liao

Chen

Siegbahn

2016

Chemistry A European J

PceA is a cobalamin-dependent reductive dehalogenase that catalyzes the dechlorination of perchloroethylene to trichloroethylene and then to cis-dichloroethylene as the sole final product. The reaction mechanism and the regioselectivity of this enzyme are investigated by using density functional calculations. Four different substrates, namely, perchloroethylene, trichloroethylene, cis-dichloroethylene, and chlorotheylene, have been considered and were found to follow the same reaction mechanism pattern. The reaction starts with the reduction of Co(II) to Co(I) through a proton-coupled electron transfer process, with the proton delivered to a Tyr246 anion. This is followed by concerted C-Cl bond heterolytic cleavage and proton transfer from Tyr246 to the substrate carbon atom, generating a Co(III) -Cl intermediate. Subsequently, a one-electron transfer leads to the formation of the Co(II) -Cl product, from which the chloride and the dehalogenated product can be released from the active site. The substrate reactivity follows the trend perchloroethylene>trichloroethylene≫cis-dichloroethylene≫chlorotheylene. The barriers for the latter two substrates are significantly higher compared with those for perchloroethylene and trichloroethylene, implying that PceA does not catalyze their degradation. In addition, the formation of cis-dichloroethylene has a lower barrier by 3.8 kcal mol(-1) than the formation of trans-dichloroethylene and 1,1-dichloroethylene, reproducing the regioselectivity. These results agree quite well with the experimental findings, which show cis-dichloroethylene as the sole product in the PceA-catalyzed dechlorination of perchloethylene and trichloroethylene.

“…The presence of a cyanobacteria bloom does not mean that the organisms are toxic or producing T&O compounds. However, the absence of toxins or T&O compounds does not mean that a problem is not emergent (Westrick & Szlag 2018). T&O compounds can be detected and quantified by selected ion monitoring (known as SIM) using GC-MS methods described by Adams and colleagues (2020).…”

Section: Microcystis and Anabaena Bloom In A Lake Arrowhead Tributary In July 2020mentioning

confidence: 99%

Successfully Detecting and Mitigating Algal Blooms and Taste and Odor Compounds

Adams¹,

Southard²,

Reeder³

et al. 2021

Journal AWWA

After receiving hundreds of complaints, the City of Wichita Falls, Texas, developed a plan for monitoring harmful algal blooms to detect and mitigate taste and odor (T&O) compounds and cyanotoxins.The plan uses sensory analysis, genuslevel or functional-group identification, gas chromatography-mass spectrometry/ electron capture detector, data sondes, and quantitative polymerase chain reaction to monitor blooms for T&O issues and cyanotoxins before they become problems.When blooms are detected, mitigation efforts include source-switching, pretreatment, oxidation, and adsorption, which have eliminated customer complaints following more than 60 years of unmitigated T&O cycles.