Hydroxymethylglutaryl co-enzyme A reductase inhibition attenuates endotoxin-mediated inflammatory responses

Background

The aim of this study was to investigate whether inhibition of hydroxymethylglutaryl co-enzyme A reductase attenuates leucocyte–endothelial cell interactions and alters expression of endothelial constitutive nitric oxide synthase (ecNOS) and inducible nitric oxide synthase (iNOS) following exposure to endotoxin.

Methods

Male Sprague–Dawley rats were randomized into control, lipopolysaccharide (LPS) and pravastatin + LPS groups (seven per group). Pravastatin sodium was gavaged at 0·4 mg per kg per day for 5 days, after which LPS 15 mg/kg was administered via the jugular vein. Intravital microscopy was used to determine leucocyte–endothelial cell interactions.

Results

Following the administration of LPS there was a significant reduction in leucocyte rolling velocity at 10 min (mean(s.e.m.) 69(3) versus 102(6) per cent of baseline value; P = 0·041), an increase in the number of adherent leucocytes at 10 min (4·5(0·5) versus 2·8(0·3) per 100 µm; P = 0·044) and an increase in the number of leucocytes undergoing transendothelial migration at 30 min (4·2(0·4) versus 1·7(0·4) per field; P = 0·008) compared with controls. Pretreatment with pravastatin significantly attenuated LPS-induced leucocyte–endothelial cell interactions (rolling velocity 89(6) per cent at 10 min, P = 0·038; adherent leucocytes 3·0(0·5) per 100 µm at 10 min, P = 0·038; migrating leucocytes 1·9(0·5) per field at 30 min, P = 0·001). This endothelial protection was associated with maintenance of ecNOS and reduced iNOS expression within mesenteric tissues.

Conclusion

These data show that pravastatin produces anti-inflammatory effects in response to injurious stimuli by attenuation of leucocyte–endothelial cell interactions.

A unique patient with an Ullrich-Turner syndrome variant and mosaicism for a tiny r(X) and a partial proximal duplication 1q

A 7-year old female with global cognitive impairment, short attention span, hyperactivity, impulsivity, and many compulsive behaviors was referred to the Genetics Clinic. Height was below the 5th centile and weight was at the 5th centile while head circumference was at the 50th centile. Minor anomalies included bluish sclera, low set and slightly posteriorly rotated auricles and a narrow palate with marked overbite. There was no significant family history. Chromosome analysis showed an unbalanced, mosaic female karyotype consisting of three cell lines: 46,X,+r[46]/45,X[37]/45,X,dup(1)(q11q21.3) [17] de novo.ish r(X)(DXZ1+,XIST+). Expression of XIST was observed in cDNA from the patient, suggesting the presence of an inactive X chromosome. Inactivation was confirmed by detection of a methylated allele of androgen receptor. This methylated allele was under-represented in undigested DNA, consistent with it arising from the r(X) which was present in only a minority of the patient's cells. The clinical phenotype of the tiny r(X) syndrome in our patient is obviously further influenced by mosaicism for the dup(1). Few cases of duplication of the proximal portion of chromosome 1 have been reported. Of these, the duplication either was present in all cells or involved different band regions so that a direct comparison would be difficult. However, the lower percentage of mosaicism for the dup(1) in our patient would suggest a milder influence on the clinical phenotype.

Intracavernosal alprostadil is effective for the treatment of erectile dysfunction in diabetic men

The efficacy and safety of intracavernosal alprostadil was evaluated for the treatment of erectile dysfunction in men with type I or type II diabetes mellitus. This was an open-label, flexible dose-escalating study involving 336 men (77% of whom were Asian/Oriental) enrolled by 15 centres in Australia, Canada and seven countries in Asia. The effective alprostadil dose, ie the dose producing penile rigidity adequate for intercourse and lasting up to 60 min, was established by titration at the clinic prior to entry into the 6 month self-treatment home phase. All men were fully trained in the self-injection technique before entry into the home phase. Efficacy and safety were assessed using patient and partner diaries and by interview at clinic visits during the titration phase and after 1, 3 and 6 months of treatment. An effective home dose was established by titration for 94% of the 336 men (median dose 20 microg, range 2.5-60 microg). Of 278 (83%) men who entered the home phase, 277 men (247 with type II diabetes and 30 with type I diabetes) had evaluable data for alprostadil dosage and clinical response. During the home phase, a satisfactory erectile response was achieved after 99% of injections, and the median alprostadil dose remained unchanged. The initial home dose and clinical response were similar in type I and type II diabetic men. Treatment was generally well tolerated with a low incidence of penile pain (24%) In conclusion, intracavernosal alprostadil was effective and well tolerated in type I and type II diabetic men with erectile dysfunction of mixed aetiology.

Expression of legumin and vicilin genes in pea mutants and the production of legumin in transgenic plants

Pea seeds contain two major storage proteins, legumin and vicilin, in proportions that are genetically and environmentally determined. They are synthesized from at least 40 genes and at least 10 different genetic loci. Mutant alleles at loci involved in starch synthesis, which result in perturbations in starch accumulation, also affect the expression of legumin genes, thereby influencing the legumin: vicilin ratio within the total seed protein. Examples of such alleles include r (starch-branching enzyme) and rb (ADP-glucose pyrophosphorylase), both of which result in a reduction in legumin synthesis; double mutants (rrb) show a particularly severe reduction in the amount of legumin. The effects of such mutations are specific to legumins. The amounts of vicilin are unaffected by mutations at r or rb. One of the consequences of the production of legumin from many genes is structural heterogeneity that is believed to preclude the purification of homogeneous legumin for crystallization and 3D-structure determination. Expression of cloned legumin cDNA in E. coli can result in sequence homogeneity, but E. coli is unable to carry out the normal proteolytic processing of legumin precursors and consequently such material is different from that produced in pea seeds. This paper describes the high-level synthesis, processing and assembly of pea legumin in transgenic wheat seeds, leading to the spontaneous in vitro formation of paracrystalline arrays of legumin, which may be attributed to the fact that the legumin consists of a single type of subunit. Such material might be used as a source of single-sequence, processed and assembled pea legumin for structural investigation.

Pea legumin overexpressed in wheat endosperm assembles into an ordered paracrystalline matrix

Legumin, a major component of pea seed storage vacuoles, is synthesized by a number of paralogous genes. The polypeptides are cleaved posttranslationally and can form mixed hexamers. This heterogeneity hampers structural studies, based on the production of hexamer crystals in vitro. To study a single type of homogenous legumin we produced pea legumin A in transgenic wheat (Triticum aestivum) endosperm where prolamins are predominant and only small amounts of globulins accumulate in separate inclusions. We demonstrated that the legumin precursor was cleaved posttranslationally and we confirmed assembly into 11S hexamers. Legumin was deposited within specific regions of the inclusion bodies. Angular legumin crystals extended from the inclusion bodies into the vacuole, correlating with the high legumin content. This suggests that the high-level production of a single type of legumin polypeptide resulted in the spontaneous formation of crystals in vivo. The use of a heterologous cereal system such as wheat endosperm to produce, isolate, and recrystallize homogenous 11S legume globulins offers exciting possibilities for structural analysis and characterization of these important seed storage proteins.

Molecular cloning and biochemical characterization of a lipoxygenase in almond (Prunus dulcis) seed

We have characterized an almond (Prunus dulcis) lipoxygenase (LOX) that is expressed early in seed development. The presence of an active lipoxygenase was confirmed by western blot analysis and by measuring the enzymatic activity in microsomal and soluble protein samples purified from almond seeds at this stage of development. The almond lipoxygenase, which had a pH optimum around 6, was identified as a 9-LOX on the basis of the isomers of linoleic acid hydroperoxides produced in the enzymatic reaction. A genomic clone containing a complete lipoxygenase gene was isolated from an almond DNA library. The 6776-bp sequence reported includes an open reading frame of 4667 bp encoding a putative polypeptide of 862 amino acids with a calculated molecular mass of 98.0 kDa and a predicted pI of 5.61. Almond seed lipoxygenase shows 71% identity with an Arabidopsis LOX1 gene and is closely related to tomato fruit and potato tuber lipoxygenases. The sequence of the active site was consistent with the isolated gene encoding a 9-LOX.

Risk-resistance adaptation model for caregivers and their children with sickle cell syndromes

This investigation examined the risk-resistance adaptation model for children with sickle cell disease and their primary caregivers. Participants were 55 children, ranging in age from 5 to 16 years with a mean age of 9 years 2 months, diagnosed with sickle cell disease and their primary caregivers, recruited from a university medical center. Measures included adjustment (i.e. primary caregiver and child adjustment), risk factors (i.e. disease and disability, functional independence, and psychosocial stressors), resistance factors (i.e. intrapersonal health locus of control, social-ecological), and stress processing (coping). Primary caregivers' adjustment was associated with developmental coping, changeR2 = .08, and child adaptation was associated with an internal health locus of control, changeR2 = .22. An indirect effect of primary caregivers' coping on child adjustment was found through influence on primary caregivers' adjustment, changeR2 = .11. The findings support research among other chronically ill populations that suggests an association between coping and disease adjustment. The results were interpreted to support the use of theoretically driven models in predicting the adaptation of children with chronic illness and adjustment in their caregivers.

Mutagenesis and modelling of linoleate-binding to pea seed lipoxygenase

We have produced a model to define the linoleate-binding pocket of pea 9/13-lipoxygenase and have validated it by the construction and characterization of eight point mutants. Three of the mutations reduced, to varying degrees, the catalytic centre activity (kcat) of the enzyme with linoleate. In two of the mutants, reductions in turnover were associated with changes in iron-coordination. Multiple sequence alignments of recombinant plant and mammalian lipoxygenases of known positional specificity, and the results from numerous other mutagenesis and modelling studies, have been combined to discuss the possible role of the mutated residues in pea 9/13-lipoxygenase catalysis. A new nomenclature for recombinant plant lipoxygenases based on positional specificity has subsequently been proposed. The null-effect of mutating pea 9/13-lipoxygenase at the equivalent residue to that which controlled dual positional specificity in cucumber 13/9-lipoxygenase, strongly suggests that the mechanisms controlling dual positional specificity in pea 9/13-lipoxygenase and cucumber 13/9-lipoxygenase are different. This was supported from modelling of another isoform of pea lipoxygenase, pea 13/9-lipoxygenase. Dual positional specificity in pea lipoxygenases is more likely to be determined by the degree of penetration of the methyl terminus of linoleate and the volume of the linoleate-binding pocket rather than substrate orientation. A single model for positional specificity, that has proved to be inappropriate for arachidonate-binding to mammalian 5-, 12- and 15-lipoxygenases, would appear to be true also for linoleate-binding to plant 9- and 13-lipoxygenases.

Probing a novel potato lipoxygenase with dual positional specificity reveals primary determinants of substrate binding and requirements for a surface hydrophobic loop and has implications for the role of lipoxygenases in tubers

A new potato tuber lipoxygenase full-length cDNA sequence (lox1:St:2) has been isolated from potato tubers and used to express in Escherichia coli and characterize a novel recombinant lipoxygenase (potato 13/9-lipoxygenase). Like most plant lipoxygenases it produced carbonyl compounds from linoleate (the preferred substrate) and was purified in the Fe(II) (ferrous) state. Typical of other potato tuber lipoxygenases, it produced 5-HPETE [5(S)-hydroperoxy-(6E, 8Z, 11Z, 14Z)-eicosatetraenoic acid] from arachidonate. In contrast to any other potato tuber lipoxygenase, it exhibited dual positional specificity and produced roughly equimolar amounts of 13- and 9-hydroperoxides (or only a slight molar excess of 9-hydroperoxides) from linoleate. We have used a homology model of pea 9/13-lipoxygenase to superimpose and compare the linoleate-binding pockets of different potato lipoxygenases of known positional specificity. We then tested this model by using site-directed mutagenesis to identify some primary determinants of linoleate binding to potato 13/9-lipoxygenase and concluded that the mechanism determining positional specificity described for a cucumber lipoxygenase does not apply to potato 13/9-lipoxygenase. This supports our previous studies on pea seed lipoxygenases for the role of pocket volume rather than inverse orientation as a determinant of dual positional specificity in plant lipoxygenases. We have also used deletion mutagenesis to identify a critical role in catalysis for a surface hydrophobic loop in potato 13/9-lipoxygenase and speculate that this may control substrate access. Although potato 13/9-lipoxygenase represents only a minor isoform in tubers, such evidence for a single lipoxygenase species with dual positional specificity in tubers has implications for the proposed role of potato lipoxygenases in the plant.

Recombinant lipoxygenases as biocatalysts for natural flavour production

We identified a lipoxygenase expressed early during almond seed development. Biochemical and molecular characterisation showed that the enzyme produces almost exclusively 9-hydroperoxides which have been demonstrated to be important factors for the production of characteristic aromas in several fruits. An almond LOX cDNA was identified by RT-PCR using RNA extracted from immature almond seeds. Sequence analysis revealed that the identified gene is closely related to tomato fruit and potato tuber lipoxygenases. The isolated cDNA was cloned into pET24a and the expression of recombinant protein was induced in E. coli. The presence of an active LOX was confirmed in cells containing the recombinant vector. HPLC analysis of the reaction products of recombinant almond LOX confirmed that the isolated cDNA encodes a 9-LOX.

Evaluation of a live, cold-passaged, temperature-sensitive, respiratory syncytial virus vaccine candidate in infancy

A live-attenuated, intranasal respiratory syncytial virus (RSV) candidate vaccine, cpts-248/404, was tested in phase 1 trials in 114 children, including 37 1-2-month-old infants-a target age for RSV vaccines. The cpts-248/404 vaccine was infectious at 104 and 105 plaque-forming units in RSV-naive children and was broadly immunogenic in children >6 months old. Serum and nasal antibody responses in 1-2 month olds were restricted to IgA, had a dominant response to RSV G protein, and had no increase in neutralizing activity. Nevertheless, there was restricted virus shedding on challenge with a second vaccine dose and preliminary evidence for protection from symptomatic disease on natural reexposure. The cpts-248/404 vaccine candidate did not cause fever or lower respiratory tract illness. In the youngest infants, however, cpts-248/404 was unacceptable because of upper respiratory tract congestion associated with peak virus recovery. A live attenuated RSV vaccine for the youngest infant will use cpts-248/404 modified by additional attenuating mutations.

An immunohistochemical analysis of fibroid vasculature

This study aimed to compare vascular parameters between fibroid and myometrium. From 10 uteri, specimens were taken from small fibroids (<0.5 cm), from the inner and outer parts of large fibroids (>3 cm), and from myometrium. Antibodies to endothelial cell markers CD31, CD34, factor VIII-related antigen (FVIII), and Ulex europaeus lectin were used in routine immuno- and lectin chemistry protocols. Parameters calculated were vascular area (VA), microvascular density (MD) and vascular luminal diameter. VA measures showed that myometrium had a greater area stained than small fibroids (P = 0.03) using CD31 and both inner (P = 0.04) and outer (P = 0.01) regions of large fibroids using FVIII, and than all groups (small, P = 0.02; inner, P = 0.02; outer, P = 0.006) using the lectin U. europaeus. MD was higher in myometrium than all uterine fibroid groups (small, P = 0.009; inner, P = 0.01; outer, P = 0.01) using U. europaeus lectin, than both regions of large (inner, P = 0.04; outer, P = 0.02) fibroids using FVIII, and than outer regions of large fibroids using CD31 (P < 0.05). There were significantly larger diameter vessels in myometrium and large fibroids compared with small fibroids using CD34, FVIII and the lectin U. europaeus (P </= 0.04). These differences in vasculature may represent differences in angiogenesis and vascular remodelling.

A novel presentation of cryptococcal infection in a renal allograft recipient

The population of immunosuppressed patients is growing rapidly because of the HIV epidemic and the rapid expansion in transplant medicine. These patients may present to a variety of clinical specialties with seemingly innocuous infections. We present here the first Irish case of primary cryptococcal cellulitis. The patient was a 62-year old renal transplant recipient and was immunosuppressed with Cyclosporine, Azathioprine and Prednisolone. He presented with an apparent bacterial cellulitis on the dorsum of the hand that had failed to respond to a 3-week course of oral antibiotics. There was no clinical evidence of systemic infection. There was tissue necrosis present and the area was debrided surgically. Histological examination of debrided tissue revealed necrotic granulomata and budding yeast-like organisms. Cryptococcus neoformans was cultured from this specimen. The patient was treated with oral fluconazole 400 mg daily for 6 weeks with complete healing of the infected area and no evidence of recurrence after 12 months of follow up. This case emphasises the need for a high index of suspicion for atypical infection in the immunocompromised patient.

Co-oxidation of beta-carotene catalyzed by soybean and recombinant pea lipoxygenases

A number of products including apocarotenal, epoxycarotenal, apocarotenone, and epoxycarotenone generated by lipoxygenase (LOX) catalyzed co-oxidation of beta-carotene have been tentatively identified through the use of GC/MS and HPLC combined with photodiode array detection. Because of the large number of high molecular weight products detected and their probable chemical structures, a co-oxidation mechanism is proposed that involves random attack along the alkene chain of the carotenoid by a LOX-generated linoleoylperoxyl radical. It is suggested that a direct release from the enzyme of the radical, which initiates the co-oxidation of beta-carotene, is greater for pea LOX-3 than for pea LOX-2 or soybean LOX-1. It is proposed that further products may be formed by free radical propagated reactions and that the formation of 1,10- and 1,14-dicarbonyl compounds may arise by secondary oxidation of the primary products.

Frequency and predictors of medically attended injuries in HIV-infected children

The extent to which medically attended injuries complicate the clinical course of HIV-infected (HIV+) children is unknown. In a cohort of HIV+ children delivered from 1985 to 1990 and aged less than 60 months, we determined medically attended injuries per 100 child-years, Injury Severity Scores (ISS), and predictors of medically attended injuries by using New York State Medicaid claims from 1986 to 1992 linked to birth certificates. Injury rates and ISS were compared to those of a population of black, inner city children aged less than 60 months from emergency room records. HIV+ children had slightly more injuries (19.3 vs. 16.8/100 child-years) but similar ISS (2.4 vs. 2.3). Predictors of injuries in HIV+ children included younger maternal age (24/100 child-years, p = 0.008) and delivery outside of New York City (29/100 child-years, p = 0.02). Illicit drug use and alcohol use were associated with greater ISS while cocaine use was associated with a higher rate of possibly intentional injuries. Medically attended injuries affected one in five HIV+ children in our cohort annually, slightly more than the comparison population. Specific maternal and birth characteristics such as substance abuse and younger age at delivery may help target at-risk children.

Molecular and clinical correlation study of Williams-Beuren syndrome: No evidence of molecular factors in the deletion region or imprinting affecting clinical outcome

Williams-Beuren syndrome (WBS) results from a deletion of 7q11.23 in 90-95% of all clinically typical cases. Clinical manifestation can be variable and therefore, deletion size, inherited elastin (ELN) and LIM kinase 1 (LIMK1) alleles, gender, and parental origin of deletion have been investigated for associations with clinical outcome. In an analysis of 85 confirmed deletion cases, no statistically significant associations were found after Bonferroni's correction for multiple pairwise comparisons. Furthermore, the present data do not support presence of imprinted genes in the WBS common deletion despite a nonsignificant excess of maternal over paternal deletions. Maternal deletion cases were more likely to have a large head circumference in the present data. Also, pairwise comparisons between individual WBS clinical features have been conducted and revealed significant associations between (1) low birth weight and poor postnatal weight gain (<10th percentile at the time of examination) and (2) transient infantile hypercalcemia and a stellate iris pattern. The latter association could indicate a common underlying etiology.

Hyperornithinaemia-hyperammonaemia-homocitrullinuria syndrome is caused by mutations in a gene encoding a mitochondrial ornithine transporter

Neurospora crassa ARG13 and Saccharomyces cerevisiae ARG11 encode mitochondrial carrier family (MCF) proteins that transport ornithine across the mitochondrial inner membrane. We used their sequences to identify EST candidates that partially encode orthologous mammalian transporters. We thereby identified such a gene (ORNT1) that maps to 13q14 and whose expression, similar to that of other urea cycle (UC) components, was high in liver and varied with changes in dietary protein. ORNT1 expression restores ornithine metabolism in fibroblasts from patients with hyperammonaemia-hyperornithinaemia-homocitrullinuria (HHH) syndrome. In a survey of 11 HHH probands, we identified 3 ORNT1 mutant alleles that account for 21 of 22 possible mutant ORNT1 genes in our patients: F188delta, which is common in French-Canadian HHH patients and encodes an unstable protein; E180K, which encodes a stable, properly targeted protein that is inactive; and a 13q14 microdeletion. Our results show that ORNT1 encodes the mitochondrial ornithine transporter involved in UC function and is defective in HHH syndrome.

Molecular analysis of a null mutant for pea (Pisum sativum L.) seed lipoxygenase-2

A mutant line of Pisum fulvum was identified that lacked seed lipoxygenase-2 (LOX-2). The mutant phenotype was introgressed into a standard Pisum sativum cv. Birte to provide near-isogenic lines with or without seed LOX-2. Genetic analyses showed the mutation to behave as a single, recessive Mendelian gene. Northern and dot-blot analyses showed a large reduction in LOX-2 mRNA from developing seeds of the LOX-2-null mutant. A restriction fragment length polymorphism associated with the 5' end of the LOX-2 gene(s) co-segregated with the null phenotype, indicating that the reduction of LOX-2 mRNA was neither a consequence of deletion of the LOX genes nor a consequence of the action of a genetically distant regulatory gene. Analysis of the 5'-flanking sequences of LOX-2 genes from Birte and the near-isogenic LOX-2-null mutant revealed a number of insertions, deletions and substitutions within the promoter from the LOX-2-null mutant that could be responsible for the null phenotype. Incubation of crude seed LOX preparations from Birte and the LOX-2-null mutant showed that the latter generated relatively less 13-hydroperoxides and also produced relatively more hydroxy- and ketoacid compounds that have implications for the fresh-frozen pea industry.

Noninvasive surgery of prostate tissue by high intensity focused ultrasound: an updated report

OBJECTIVE

To establish clinical efficacy and safety of High Intensity Focused Ultrasound (HIFU) for the treatment of benign prostatic hyperplasia (BPH) in a multiple site clinical study.

METHODS

Seven clinical sites were set up for the studies, five in the USA, one in Canada and one in Japan respectively. Sixty two patients were enrolled in these three studies. Transrectal ultrasound probes made to produce sufficient acoustic power required for focused ultrasound surgery of the prostate as well as to perform imaging of the prostate, were employed in the study. The probes ware made of 2.5, 3.0, 3.5, 4.0 and 4.5 cm focal length transducers to treat varying prostate sizes and shapes and operated at 4 MHz frequency for both imaging and treatment. The employed ultrasound device produced both transverse and longitudinal images of the prostate on the same display. The images were used for selection of tissue volume, treatment planning and monitoring of tissue during the HIFU treatment cycle. The patients in the USA and Canada were followed for two years and those in Japan were followed for one year on a regular interval. The results were evaluated for changes in the peak flow rate (Qmax in ml/s), quality of life (QOL) and International Prostate Symptom Score (IPSS).

RESULTS

The average pre / post treatment results at 180 days were significantly different for Qmax, QOL and IPSS 8.5/14.2 (ml/s), 4.7/2.1 and 22/10 respectively.

CONCLUSION

Under this protocol, HIFU was found safe and efficacious for the treatment of BPH. The HIFU treatment produced statistically significant results for the parameters measured with least complications. Additionally, the HIFU treatment was found to be durable.

Photodynamic therapy for corneal neovascularization

BACKGROUND AND OBJECTIVE

Photodynamic therapy with tin ethyl etiopurpurin (SnET2) was evaluated as a treatment modality for rat corneal neovascularization.

MATERIALS AND METHODS

Escalating light doses at 664 nm were applied focally to corneal neovascularization in rats 10 minutes following an intravenous injection of SnET2 using a low-power diode laser. Controls consisted of light-only and drug-only treatments. Clinical, angiographic, and histopathologic evaluations were performed on the animals up to 28 days after drug and/or light treatment.

RESULTS

A drug and light dose-response was seen in producing neovessel closure. In animals treated with SnET2 and the highest light dose (25 J/cm2), all eyes showed occlusion at every follow-up evaluation up to 28 days. Control eyes demonstrated progressive disease at all time points.

CONCLUSIONS

Photodynamic therapy appears to be safe and effective for eliciting prolonged (> 28 days) occlusion of corneal neovascularization in the rat model with minimal side effects and good clinical outcomes.

Characterization of authentic recombinant pea-seed lipoxygenases with distinct properties and reaction mechanisms

The two major isoforms of lipoxygenase (LOX-2 and LOX-3) from pea (Pisum sativum L. cv. Birte) seeds have been cloned and expressed from full-length cDNAs as soluble, active, non-fusion proteins in Escherichia coli. A comparison of both isoforms purified to apparent homogeneity from E. coli and pea seeds has confirmed the authenticity of the recombinant products and established the properties of the native enzymes. Despite 86% similarity at the amino acid sequence level, the enzymes have distinct properties. They have been characterized in terms of specific activity, Fe content, optimum pH, substrate and product specificity, apparent Km and Vmax for the preferred substrate, linoleic acid, and interfacial behaviour with linoleic acid. We have used this evidence, in addition to EPR spectroscopy of the hydroperoxide-activated enzymes and estimates of kcat/Km, to propose different reaction mechanisms for linoleic acid oxidation for the two isoforms. The differences relate primarily to carbonyl production from linoleic acid for which we propose a mechanism. This implicates the release of a peroxyl radical in an aerobic hydroperoxidase reaction, as the source of the carbonyl compounds formed by dismutation of the liberated peroxyl radical.