Detection of N-acetyl methionine in human and murine brain and neuronal and glial derived cell lines

N-Acetylglutamate and N-acetylmethionine compromise mitochondrial bioenergetics homeostasis and glutamate oxidation in brain of developing rats: Potential implications for the pathogenesis of ACY1 deficiency

Aminoacylase 1 (ACY1) deficiency is an inherited metabolic disorder biochemically characterized by high urinary concentrations of aliphatic N-acetylated amino acids and associated with a broad clinical spectrum with predominant neurological signs. Considering that the pathogenesis of ACY1 is practically unknown and the brain is highly dependent on energy production, the in vitro effects of N-acetylglutamate (NAG) and N-acetylmethionine (NAM), major metabolites accumulating in ACY1 deficiency, on the enzyme activities of the citric acid cycle (CAC), of the respiratory chain complexes and glutamate dehydrogenase (GDH), as well as on ATP synthesis were evaluated in brain mitochondrial preparations of developing rats. NAG mildly inhibited mitochondrial isocitrate dehydrogenase 2 (IDH2) activity, moderately inhibited the activities of isocitrate dehydrogenase 3 (IDH3) and complex II-III of the respiratory chain and markedly suppressed the activities of complex IV and GDH. Of note, the NAG-induced inhibitory effect on IDH3 was competitive, whereas that on GDH was mixed. On the other hand, NAM moderately inhibited the activity of respiratory complexes II-III and GDH activities and strongly decreased complex IV activity. Furthermore, NAM was unable to modify any of the CAC enzyme activities, indicating a selective effect of NAG toward IDH mitochondrial isoforms. In contrast, the activities of citrate synthase, α-ketoglutarate dehydrogenase, malate dehydrogenase, and of the respiratory chain complexes I and II were not changed by these N-acetylated amino acids. Finally, NAG and NAM strongly decreased mitochondrial ATP synthesis. Taken together, the data indicate that NAG and NAM impair mitochondrial brain energy homeostasis.

Disturbance of mitochondrial functions caused by N-acetylglutamate and N-acetylmethionine in brain of adolescent rats: Potential relevance in aminoacylase 1 deficiency

Aminoacylase 1 (ACY1) deficiency is a rare genetic disorder that affects the breakdown of short-chain aliphatic N-acetylated amino acids, leading to the accumulation of these amino acid derivatives in the urine of patients. Some of the affected individuals have presented with heterogeneous neurological symptoms such as psychomotor delay, seizures, and intellectual disability. Considering that the pathological mechanisms of brain damage in this disorder remain mostly unknown, here we investigated whether major metabolites accumulating in ACY1 deficiency, namely N-acetylglutamate (NAG) and N-acetylmethionine (NAM), could be toxic to the brain by examining their in vitro effects on important mitochondrial properties. We assessed the effects of NAG and NAM on membrane potential, swelling, reducing equivalents, and Ca2+ retention capacity in purified mitochondrial preparations obtained from the brain of adolescent rats. NAG and NAM decreased mitochondrial membrane potential, reducing equivalents, and calcium retention capacity, and induced swelling in Ca2+-loaded brain mitochondria supported by glutamate plus malate. Notably, these changes were completely prevented by the classical inhibitors of mitochondrial permeability transition (MPT) pore cyclosporin A plus ADP and by ruthenium red, implying the participation of MPT and Ca2+ in these effects. Our findings suggest that NAG- and NAM-induced disruption of mitochondrial functions involving MPT may represent relevant mechanisms of neuropathology in ACY1 deficiency.

E. coli Secretome Metabolically Modulates MDA-MB-231 Breast Cancer Cells' Energy Metabolism

Breast cancer (BC) is commonly diagnosed in women. BC cells are associated with altered metabolism, which is essential to support their energetic requirements, cellular proliferation, and continuous survival. The altered metabolism of BC cells is a result of the genetic abnormalities of BC cells. Risk factors can also enhance it, including age, lifestyle, hormone disturbances, etc. Other unknown BC-promoting risk factors are under scientific investigation. One of these investigated factors is the microbiome. However, whether the breast microbiome found in the BC tissue microenvironment can impact BC cells has not been studied. We hypothesized that E. coli, part of a normal breast microbiome with more presence in BC tissue, secretes metabolic molecules that could alter BC cells' metabolism to maintain their survival. Thus, we directly examined the impact of the E. coli secretome on the metabolism of BC cells in vitro. MDA-MB-231 cells, an in vitro model of aggressive triple-negative BC cells, were treated with the E. coli secretome at different time points, followed by untargeted metabolomics analyses via liquid chromatography-mass spectrometry to identify metabolic alterations in the treated BC cell lines. MDA-MB-231 cells that were not treated were used as controls. Moreover, metabolomic analyses were performed on the E. coli secretome to profile the most significant bacterial metabolites affecting the metabolism of the treated BC cell lines. The metabolomics results revealed about 15 metabolites that potentially have indirect roles in cancer metabolism that were secreted from E. coli in the culture media of MDA-MB-231 cells. The cells treated with the E. coli secretome showed 105 dysregulated cellular metabolites compared to controls. The dysregulated cellular metabolites were involved in the metabolism of fructose and mannose, sphingolipids, amino acids, fatty acids, amino sugar, nucleotide sugar, and pyrimidine, which are vital pathways required for the pathogenesis of BC. Our findings are the first to show that the E. coli secretome modulates the BC cells' energy metabolism, highlighting insights into the possibility of altered metabolic events in BC tissue in the actual BC tissue microenvironment that are potentially induced by the local bacteria. Our study provides metabolic data that could be as a basis for future studies searching for the underlying mechanisms mediated by bacteria and their secretome to alter the metabolism of BC cells.

Plasma methionine appearance and residual potential of supplemented N-acetyl-L-methionine through ruminal or abomasal infusion in dairy cows

The present study investigated the plasma methionine (Met) and residual potential of N-acetyl-L-Met (NALM) in lactating dairy cows. Six cows (75 ± 20.1 days-in-milk) were used in a replicated 3 × 3 Latin square design. Within each square, cows were randomly assigned to a sequence of three dietary treatments during each of the three 13-day periods (10 days of treatment adaptation and 3 days of data collection and sampling). The three dietary treatments are as follows: basal diet without NALM (control); control diet with 30 g/day of NALM by rumen placement (30NALM), and control diet with 60 g/day of NALM by rumen placement (60NALM). Rumen NALM dosing led to a linear increase in plasma Met concentration. Abomasal infusion with NALM resulted in both linear and quadratic increases in plasma Met concentration. No NALM was detected in milk, liver, plasma, and muscle samples after rumen placement or abomasal infusion. Supplementation of NALM did not affect dry matter intake and milk yield. The absence of plasma NALM and increases in plasma Met concentration for both ruminal and abomasal NALM dosing suggest that NALM supplemented by either rumen placement or abomasal infusion to lactating dairy cows is deacetylated before entering the central circulation.

ACY1 regulating PTEN/PI3K/AKT signaling in the promotion of non-small cell lung cancer progression

Background

Non-small cell lung cancer (NSCLC) has a poor prognosis and is the most common cause of cancer-related deaths worldwide. Aminoacylase 1 (ACY1) plays a promoting role in some cancers, but its role in NSCLC is still unclear.

Methods

Immunohistochemistry, Reverse transcription-polymerase chain reaction (RT-PCR) and western blotting assays were used to determine ACY1 expression patterns in NSCLC tissues and cell lines. The clinical significance of ACY1 in NSCLC was evaluated by χ² test and Kaplan-Meier analysis. MTT, flow cytometry, wound healing, and Transwell assays were performed to assess cell growth, apoptosis, migration, invasion, and tumorigenesis under different treatments. Male athymic BALB/C nude mice were used for xenotransplantation experiments.

Results

The results showed that ACY1 expression was elevated in NSCLC tissue samples and cells, and high ACY1 expression predicted an advanced clinical process and shorter overall survival in patients with NSCLC. Overexpression of ACY1 significantly increased cell growth, migration, invasion, and tumorigenesis, and reduced cell apoptosis, indicating that ACY1 functions as an oncogene in NSCLC. Moreover, ACY1 decreased phosphatase and tensin homolog (PTEN) expression, increased its ubiquitination, and activated PI3K/AKT signaling. Overexpression of PTEN diminished the effects of ACY1 upregulation on cell tumorigenesis promotion.

Conclusions

This study reveals that ACY1 may promote the progression of NSCLC via activating PI3K/AKT signaling in a PTEN-dependent manner. Our study may provide a better understanding of the pathogenesis and development of NSCLC.

Characterization of the ABC methionine transporter from Neisseria meningitidis reveals that lipidated MetQ is required for interaction

NmMetQ is a substrate-binding protein (SBP) from Neisseria meningitidis that has been identified as a surface-exposed candidate antigen for meningococcal vaccines. However, this location for NmMetQ challenges the prevailing view that SBPs in Gram-negative bacteria are localized to the periplasmic space to promote interaction with their cognate ABC transporter embedded in the bacterial inner membrane. To elucidate the roles of NmMetQ, we characterized NmMetQ with and without its cognate ABC transporter (NmMetNI). Here, we show that NmMetQ is a lipoprotein (lipo-NmMetQ) that binds multiple methionine analogs and stimulates the ATPase activity of NmMetNI. Using single-particle electron cryo-microscopy, we determined the structures of NmMetNI in the presence and absence of lipo-NmMetQ. Based on our data, we propose that NmMetQ tethers to membranes via a lipid anchor and has dual function and localization, playing a role in NmMetNI-mediated transport at the inner membrane and moonlighting on the bacterial surface.

Targeted metabolomics reveals dynamic portrayal of amino acids and derivatives in triple-negative breast cancer cells and culture media

Triple-negative breast cancer (TNBC) is well-known for its metastatic aggressiveness and poor survival prognosis, accounting for nearly a quarter of cases in breast cancer. We performed intra- and extra-cellular profiling of 40 amino acids and derivatives on three cell lines and their culture media, including TNBC, non-TNBC and normal breast epithelial cells, using HILIC-MS/MS. Characteristic metabolic alteration of amino acids and derivatives was observed in TNBC cells, compared to non-TNBC cells, especially in correlated intra- and extra-cellular metabolic pathways. Intra-cellularly, quantified glutamic acid, β-alanine, aspartic acid, glutathione, N-acetyl-serine and N-acetyl-methionine were most significantly increased (>2-fold, p < 0.01 and VIP > 1) in TNBC cells. Extra-cellularly, significantly increased uptake of glutamine, serine, β-alanine, and lysine and elevated excretion of glutamic acid and l-cysteine-glutathione (p < 0.01 and VIP > 1) were observed by TNBC cells from or to their cell culture media. This study depicted a novel dynamic portrayal of metabolic dysregulation between TNBC and non-TNBC cells, correlated in both intra- and extra-cellular amino acid profiles. Quantification of these distinctive metabolites of TNBC cells might offer advanced understanding and new treatment targets for TNBC.

Targeted lipidomics and metabolomics evaluations of cortical neuronal stress in schizophrenia

BACKGROUND

Cortical neuronal dysfunction has been proposed to underlie the psychopathology and cognitive dysfunction of schizophrenia. Previously we have reported altered sphingolipid and N-acylphosphatidylserine (NAPS) metabolism in the frontal cortex in schizophrenia. We continue to expand these investigations to define the biochemical basis for these critical neuropathologies.

METHODS

We undertook a targeted high resolution mass spectrometric analysis to validate our previous reports of elevated sphingolipids and NAPS in the frontal cortex of a new cohort of schizophrenia subjects. Furthermore we expanded these analyses to include ceramides, N-acylphosphatidylethanolamines (NAPE), and N-acylethanolamines (NAE). In the same tissue samples we examined N-acetylaspartylglutamate (NAAG), a modulator of excitatory amino acid transmission, hypothesized to be involved in the pathology of schizophrenia.

RESULTS

We repeated our observations of elevated sulfatides in the frontal cortex in schizophrenia. An in-depth analysis of other sphingolipids revealed decrements in ceramide levels and increased levels of lactosylceramides. NAPS also were found to be augmented in schizophrenia as we previously reported. In addition, levels of NAPES, established biomarkers of neuronal stress, were elevated while their metabolites, NAEs were decreased. With regard to excitatory amino acid neurotransmission, NAAG levels were decreased by 50% while the metabolic precursor, N-acetylaspartate was unaltered.

CONCLUSIONS

Our data support the concept of cortical neuronal dysfunction in schizophrenia as indicated by altered metabolism of structural sphingolipids and NAAG, a modulator of excitatory amino acid neurotransmission.

Reappraisal of Human HOG and MO3.13 Cell Lines as a Model to Study Oligodendrocyte Functioning

Myelination of neuronal axons is essential for proper brain functioning and requires mature myelinating oligodendrocytes (myOLs). The human OL cell lines HOG and MO3.13 have been widely used as in vitro models to study OL (dys) functioning. Here we applied a number of protocols aimed at differentiating HOG and MO3.13 cells into myOLs. However, none of the differentiation protocols led to increased expression of terminal OL differentiation or myelin-sheath formation markers. Surprisingly, the applied protocols did cause changes in the expression of markers for early OLs, neurons, astrocytes and Schwann cells. Furthermore, we noticed that mRNA expression levels in HOG and MO3.13 cells may be affected by the density of the cultured cells. Finally, HOG and MO3.13 co-cultured with human neuronal SH-SY5Y cells did not show myelin formation under several pro-OL-differentiation and pro-myelinating conditions. Together, our results illustrate the difficulty of inducing maturation of HOG and MO3.13 cells into myOLs, implying that these oligodendrocytic cell lines may not represent an appropriate model to study the (dys)functioning of human (my)OLs and OL-linked disease mechanisms.

Comparative Protective Effects of N-Acetylcysteine, N-Acetyl Methionine, and N-Acetyl Glucosamine against Paracetamol and Phenacetin Therapeutic Doses-Induced Hepatotoxicity in Rats

BACKGROUND AND AIMS

Both paracetamol (PA) and phenacetin (PH) are analgesic and antipyretic agents. Part of phenacetin therapeutic activity is attributed to its metabolism into paracetamol. Paracetamol causes direct hepatic oxidative stress damage. The present study aimed to investigate the possible damaging effects of both PA and PH, when used in therapeutic doses, on rat liver and to compare the antioxidant and hepatoprotective effects of N-acetylcysteine (NAC), N-acetyl-methionine (NAM), and N-acetylglucosamine (NAG) against PA- or PH-induced hepatic damage.

METHODS

90 male Wistar albino rats (120-140 gm) were undertaken, categorized randomly into 9 groups of 10 rats each, and administered by gavage for 2 weeks with DMSO 1% (controls), PA, PA+NAC, PA+NAM, PA+NAG, PH, PH+NAC, PH+NAM, and PH+NAG. Biochemical assays of malondialdehyde (MDA), nitric oxide (NO), reduced glutathione (GSH), total thiols, and alpha-fetoprotein (AFP) in liver homogenates and serum assays of ALT, AST, 8-hydroxy guanine (8-OH-Gua), and AFP were done. Also histopathological examinations of liver tissues in various groups were done.

RESULTS

PA and PH cause significant increase in hepatic levels of MDA, NO, and AFP and serum ALT, AST, and 8-OH-Gua levels, with significant decrease in hepatic GSH and total thiols. NAG and NAC significantly improve the PA- and PH-induced hepatic and blood, biochemical, and histopathological disturbances, respectively.

CONCLUSIONS

Both PA and PH induce oxidative stress in rat liver within their therapeutic doses. NAG and NAC in pharmacological doses can antagonize the oxidative damaging effect of both PA and PH.

Pilot Metabolome-Wide Association Study of Benzo(a)pyrene in Serum From Military Personnel

OBJECTIVE

A pilot study was conducted to test the feasibility of using Department of Defense Serum Repository (DoDSR) samples to study health and exposure-related effects.

METHODS

Thirty unidentified human serum samples were obtained from the DoDSR and analyzed for normal serum metabolites with high-resolution mass spectrometry and serum levels of free benzo(a)pyrene (BaP) by gas chromatography-mass spectrometry. Metabolic associations with BaP were determined using a metabolome-wide association study (MWAS) and metabolic pathway enrichment.

RESULTS

The serum analysis detected normal ranges of glucose, selected amino acids, fatty acids, and creatinine. Free BaP was detected in a broad concentration range. MWAS of BaP showed associations with lipids, fatty acids, and sulfur amino acid metabolic pathways.

CONCLUSION

The results show that the DoDSR samples are of sufficient quality for chemical profiling of DoD personnel.

Antibiotic Treatment Preventing Necrotising Enterocolitis Alters Urinary and Plasma Metabolomes in Preterm Pigs

Necrotising enterocolitis (NEC) is a serious gut inflammatory condition in premature neonates, onset and development of which depend on the gut microbiome. Attenuation of the gut microbiome by antibiotics can reduce NEC incidence and severity. However, how the antibiotics-suppressed gut microbiome affects the whole-body metabolism in NEC-sensitive premature neonates is unknown. In formula-fed preterm pigs, used as a model for preterm infants, plasma and urinary metabolomes were investigated by LC-MS and ¹H NMR, with and without antibiotic treatment immediately after birth. While it reduced the gut microbiome density and NEC lesions as previously reported, the antibiotic treatment employed in the current study affected the abundance of 44 metabolites in different metabolic pathways. In antibiotics-treated pigs, tryptophan metabolism favored the kynurenine pathway, relative to the serotonin pathway, as shown by specific metabolites. Metabolites associated with the gut microbiome, including 3-phenyllactic acid, 4-hydroxyphenylacetic acid, and phenylacetylglycine, all from phenylalanine, and three bile acids showed lower levels in the antibiotics-treated pigs where the gut microbiome was extensively attenuated. Findings in the current study warrant further investigation of metabolic and developmental consequences of antibiotic treatment in preterm neonates.

Metabolic Serum Profiles for Patients Receiving Allogeneic Stem Cell Transplantation: The Pretransplant Profile Differs for Patients with and without Posttransplant Capillary Leak Syndrome

Allogeneic stem cell transplantation is commonly used in the treatment of younger patients with severe hematological diseases, and endothelial cells seem to be important for the development of several posttransplant complications. Capillary leak syndrome is a common early posttransplant complication where endothelial cell dysfunction probably contributes to the pathogenesis. In the present study we investigated whether the pretreatment serum metabolic profile reflects a risk of posttransplant capillary leak syndrome. We investigated the pretransplant serum levels of 766 metabolites for 80 consecutive allotransplant recipients. Patients with later capillary leak syndrome showed increased pretherapy levels of metabolites associated with endothelial dysfunction (homocitrulline, adenosine) altered renal regulation of fluid and/or electrolyte balance (betaine, methoxytyramine, and taurine) and altered vascular function (cytidine, adenosine, and methoxytyramine). Additional bioinformatical analyses showed that capillary leak syndrome was also associated with altered purine/pyrimidine metabolism (i.e., metabolites involved in vascular regulation and endothelial functions), aminoglycosylation (possibly important for endothelial cell functions), and eicosanoid metabolism (also involved in vascular regulation). Our observations are consistent with the hypothesis that the pretransplant metabolic status can be a marker for posttransplant abnormal fluid and/or electrolyte balance.

Metabolomics analysis identifies novel plasma biomarkers of cystic fibrosis pulmonary exacerbation

BACKGROUND

Cystic fibrosis (CF) lung disease is characterized by infection, inflammation, lung function decline, and intermittent pulmonary exacerbations. However, the link between pulmonary exacerbation and lung disease progression remains unclear. Global metabolomic profiling can provide novel mechanistic insight into a disease process in addition to putative biomarkers for future study. Our objective was to investigate how the plasma metabolomic profile changes between CF pulmonary exacerbation and a clinically well state.

METHODS

Plasma samples and lung function data were collected from 25 CF patients during hospitalization for a pulmonary exacerbation and during quarterly outpatient clinic visits. In collaboration with Metabolon, Inc., the metabolomic profiles of matched pair plasma samples, one during exacerbation and one at a clinic visit, were analyzed using gas and liquid chromatography coupled with mass spectrometry. Compounds were identified by comparison to a library of standards. Mixed effects models that controlled for nutritional status and lung function were used to test for differences and principal components analysis was performed.

RESULTS

Our population had a median age of 27 years (14-39) and had a median FEV1 % predicted of 65% (23-105%). 398 total metabolites were identified and after adjustment for confounders, five metabolites signifying perturbations in nucleotide (hypoxanthine), nucleoside (N4-acetylcytidine), amino acid (N-acetylmethionine), carbohydrate (mannose), and steroid (cortisol) metabolism were identified. Principal components analysis provided good separation between the two clinical phenotypes.

CONCLUSIONS

Our findings provide putative metabolite biomarkers for future study and allow for hypothesis generation about the pathophysiology of CF pulmonary exacerbation.

Growth of bulk single crystal of N-acetyl DL-methionine and its spectral characterization

Bulk size single crystal of N-acetyl DL-methionine (C7H13NO3S) (1) was grown using a home-made crystal growth setup (MKN setup). The identity of the grown crystal was confirmed by single crystal X-ray diffraction. The modes of vibrations of the functional groups present were assigned using the infrared (IR) spectrum. UV-vis-NIR spectra showed that the crystals have excellent transparency in the visible and infrared regions. The thermal stability and decomposition of the sample was studied by using thermal analysis (TGA/DTA). Photoluminescence excitation studies showed that the emission occurred at 350 nm for the compound.

Isolated mild intellectual disability expands the aminoacylase 1 phenotype spectrum

Aminoacylase 1 (ACY1) deficiency is a rare inborn error of metabolism presenting with heterogeneous neurological symptoms such as psychomotor delay, seizures, intellectual disability and it is characterized by increased urinary excretion of N-acetylated amino acids. We report on a new patient who presented ACY1 deficiency in association with isolated mild intellectual disability, but neither neurological symptoms nor autistic features. The child showed a compound heterozygous mutation (p.Glu233Asp) and a novel p.Ser192Arg fs*64, predicting an unstable transcript and resulting in very low protein levels.This new ACY1 deficient child was identified through regular screening for inborn error of metabolism adopted in our department in all cases of intellectual disability. This report supports a recommendation to perform metabolic investigations in patients with isolated mild intellectual disability.

Long-term differential changes in mouse intestinal metabolomics after γ and heavy ion radiation exposure

Tissue consequences of radiation exposure are dependent on radiation quality and high linear energy transfer (high-LET) radiation, such as heavy ions in space is known to deposit higher energy in tissues and cause greater damage than low-LET γ radiation. While radiation exposure has been linked to intestinal pathologies, there are very few studies on long-term effects of radiation, fewer involved a therapeutically relevant γ radiation dose, and none explored persistent tissue metabolomic alterations after heavy ion space radiation exposure. Using a metabolomics approach, we report long-term metabolomic markers of radiation injury and perturbation of signaling pathways linked to metabolic alterations in mice after heavy ion or γ radiation exposure. Intestinal tissues (C57BL/6J, female, 6 to 8 wks) were analyzed using ultra performance liquid chromatography coupled with electrospray quadrupole time-of-flight mass spectrometry (UPLC-QToF-MS) two months after 2 Gy γ radiation and results were compared to an equitoxic ⁵⁶Fe (1.6 Gy) radiation dose. The biological relevance of the metabolites was determined using Ingenuity Pathway Analysis, immunoblots, and immunohistochemistry. Metabolic profile analysis showed radiation-type-dependent spatial separation of the groups. Decreased adenine and guanosine and increased inosine and uridine suggested perturbed nucleotide metabolism. While both the radiation types affected amino acid metabolism, the ⁵⁶Fe radiation preferentially altered dipeptide metabolism. Furthermore, ⁵⁶Fe radiation caused upregulation of ‘prostanoid biosynthesis’ and ‘eicosanoid signaling’, which are interlinked events related to cellular inflammation and have implications for nutrient absorption and inflammatory bowel disease during space missions and after radiotherapy. In conclusion, our data showed for the first time that metabolomics can not only be used to distinguish between heavy ion and γ radiation exposures, but also as a radiation-risk assessment tool for intestinal pathologies through identification of biomarkers persisting long after exposure.

Oxyhalogen–Sulfur Chemistry: Kinetics and Mechanism of Oxidation of N-Acetyl-ʟ-methionine by Aqueous Iodine and Acidified Iodate

The use of N-acetyl-l-methionine (NAM) as a bio-available source for methionine supplementation as well as its ability to reduce the toxicity of acetaminophen poisoning has been reported. Its interaction with the complex physiological matrix, however, has not been thoroughly investigated. This manuscript reports on the kinetics and mechanism of oxidation of NAM by acidic iodate and aqueous iodine. Oxidation of NAM proceeds by a two electron transfer process resulting in formation of a sole product: N-acetyl-l-methionine sulfoxide (NAMS=O). Data from electrospray ionization mass spectrometry confirmed the product of oxidation as NAMS=O. The stoichiometry of the reaction was deduced to be IO3– + 3NAM → I– + 3NAMS=O. In excess iodate, the stoichiometry was deduced to be 2IO3– + 5NAM + 2H+ → I2 + 5NAMS=O + H2O. The reaction between aqueous iodine and NAM gave a 1 : 1 stoichiometric ratio: NAM + I2 + H2O → NAMS=O + 2I– + H+. This reaction was relatively rapid when compared with that between NAM and iodate. It did, however, exhibit some auto-inhibitory effects through the formation of triiodide (I3–) which is a relatively inert electrophile when compared with aqueous iodine. A simple mechanism containing 11 reactions gave a reasonably good fit to the experimental data.