RESUMEN
Hereditary coproporphyria (HCP) and variegate porphyria (VP) are referred to as neurocutaneous porphyrias (NCP). Data concerning their systemic presentation are limited and no direct attempt of comparison of the two has ever been made. Our aim was to describe the type and frequency of systemic manifestations of NCPs in Israeli patients. A cross-sectional survey was conducted. The study population included all patients with NCP diagnosed at the Israeli National Service for Biochemical Diagnoses of Porphyrias (INSP) between 1988 and 2019. Of the 83 patients with NCP who were alive in 2019, 61 (73%) completed the survey, 40 with VP and 21 with HCP. Systemic symptoms were reported by 63% of the VP group and 62% of the HCP group (p = .96); corresponding rates of cutaneous symptoms were 58% and 5% (p < .001). We found no association between the occurrence of systemic and cutaneous symptoms. Among patients with systemic involvement, abdominal pain was the predominant systemic symptom, found in 64% of the VP group and 69% of the HCP group; Analysis of symptom frequency showed that in 68% of the VP group, systemic symptoms (either abdominal, musculoskeletal or neuropsychiatric) occurred on a daily/weekly basis, whereas the HCP group experienced less than one symptom per week (p < .001). This nationwide study depicts a significantly heavier disease burden in VP patients compared to HCP owing to its more frequent neurovisceral and cutaneous manifestations.
RESUMEN
Protoporphyrinogen oxidase (PPOX), the penultimate enzyme in the haem biosynthetic pathway catalysers the six electron oxidation of protoporphyrinogen-IX to protoporphyrin-IX, in the presence of flavin adenine dinucleotide (FAD) and oxygen. In humans, partial defects in PPOX result in variegate porphyria. In this study, the FAD binding region in Myxococcus xanthus PPOX was analysed by engineering and characterising a selection of mutant proteins. Amino acid residues which interact with FAD via their side chains were selected for study. Mutants were characterised and compared with wild type protein. Characterisation included FAD quantitation, analysis of FAD spectra and kinetic assay. Results revealed that Serine 20 mutants could still bind FAD, but polarity in this position is favourable, yet not essential for the integrity of FAD binding. Study of Glutamate 39 mutants suggest that a negative charge at position 39 is clearly favoured for interaction with the ribose ring of FAD, as all non-conservative replacements could not bind sufficient FAD. Asparagine 441 appears not to be directly involved in FAD binding but rather in stabilizing the FAD, and polarity in this position appears important. Tryptophan 408 may play a role in orientating or stabilizing the bound substrate during catalysis, and a non-polar (or slightly polar) residue is favoured at this position; however, aromaticity in this position appears not to be critical. Overall this study sheds further light on how M. xanthus PPOX interacts with FAD.