Tyrosinase is a monooxygenase that catalyzes both the hydroxylation of p-hydroxyphenyl moieties to o-catechols and the oxidation of o-catechols to o-quinones. Apart from its critical functionality in melanogenesis and the synthesis of various neurotransmitters, this enzyme is also used in a variety of biotechnological applications, most notably mediating covalent cross-linking between polymers containing p-hydroxyphenyl groups, forming a hydrogel. Tyrosinases from the genus Streptomyces are usually secreted as a complex with their caddie protein. In this study, we report an increased secretion efficiency observed when the Streptomyces antibioticus tyrosinase gene melC2 was introduced into Pseudomonas fluorescens along with its caddie protein gene melC1, which has the DNA sequence for the Tat (twin-arginine translocation) signal.
IMPORTANCE We observed that the S. antibioticus extracellular tyrosinase secretion level was even higher in its nonnatural translationally conjugated fusion protein form than in the natural complex of two separated polypeptides. The results of this study demonstrate that tyrosinase-expressing P. fluorescens can be a stable source of bacterial tyrosinase through exploiting the secretory machinery of P. fluorescens.
A 20-year-old man presented with sleep apnea. Polysomnography was performed and it revealed nine apneas and two hypopneas. Contrary to typical apnea, however, rhythmic epileptiform discharges appeared at bifrontal area on EEG just before the start of apnoea. Video-EEG monitoring was performed to classify these events, and to evaluate the relationship of apnoea and ictal discharge. Ictal EEG revealed paroxysmal fast activity over the bifrontal area. Ictal SPECT showed hyperperfusion in right frontal area. Given these findings, we concluded that these events were epileptic seizures presenting as obstructive sleep apnea. Antiepileptic medication was initiated, and the events were decreased. This case demonstrates that nocturnal frontal love epilepsy may be the potential cause of obstructive sleep apnea (OSA).
Rapid eye movement (REM) sleep behavior disorder (RBD) is characterized by dream-enacting behaviors during REM sleep. However, many sleep disorders can produce RBD mimicking symptoms, also known as 'pseudo-RBD'. We report a patient with severe obstructive sleep apnea with 'pseudo-RBD' symptoms that were eliminated by continuous positive airway pressure treatment. Polysomnography is mandatory to establish the proper diagnosis of RBD.
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