Examination of Subbasal Nerve Plexus and Central Corneal Stromal Microstructure in Subjects With Congenital Aniridia, Using in Vivo Confocal Laser Scanning Microscopy.

PURPOSE: During life up to 70% of aniridia subjects develop aniridia-associated keratopathy (AAK). AAK is characterized by limbal stem cell insufficiency, impaired corneal epithelial cell differentiation and abnormal cell adhesion, which leads to centripetal spreading vascularization, conjunctivalization, and thickening of the cornea. Our aim was to examine the subbasal nerve plexus and central corneal stromal microstructure in subjects with congenital aniridia, using in vivo confocal laser scanning microscopy CLSM. METHODS: 31 eyes of 18 patients (55.6% males, mean age: 25.22 ± 16.35 years) with congenital aniridia and 46 eyes of 29 healthy subjects (41.4% males, mean age 30 ± 14.82 years) were examined using the Rostock Cornea Module of Heidelberg Retina Tomograph-III. At the subbasal nerve plexus, corneal nerve fiber density (CNFD), corneal nerve fiber length (CNFL), corneal total branch density (CTBD), and corneal nerve fiber width (CNFW) were analyzed using ACCMetrics software. Keratocyte density in the anterior, middle and posterior stroma was assessed manually. RESULTS: The CNFD (2.02 ± 4.08 vs 13.99 ± 6.34/mm2), CNFL (5.78 ± 2.68 vs 10.56 ± 2.82 mm/mm2) and CTBD (15.08 ± 15.62 vs 27.44 ± 15.05/mm2) were significantly lower in congenital aniridia subjects than in controls (p < 0.001 for all). CNFW was significantly higher in aniridia subjects than in controls (0.03 ± 0.004 vs 0.02 ± 0.003 mm/mm2) (p = 0.003). Keratocyte density was significantly lower in all stromal layers of aniridia subjects than in controls (p < 0.001 for all). Stromal alterations included confluent keratocytes, keratocytes with long extensions and hyperreflective dots between keratocytes in aniridia. CONCLUSIONS: Decrease in CNFD, CNFL, and CTBD, as well as increase in CNFW well refer to the congenital aniridia-associated neuropathy. The decreased keratocyte density and the stromal alterations may be related to an increased cell death in congenital aniridia, nevertheless, stromal changes in different stages of AAK have to be further analyzed in detail.

Evaluation of Retinal Blood Flow in Patients with Monoclonal Gammopathy Using OCT Angiography.

BACKGROUND: Monoclonal gammopathy (MG) is characterized by monoclonal protein overproduction, potentially leading to the development of hyperviscosity syndrome. OBJECTIVE: To assess retinal circulation using optical coherence tomography angiography (OCTA) parameters in patients with monoclonal gammopathy. METHODS: OCTA measurements were performed using the Optovue AngioVue system by examining 44 eyes of 27 patients with MG and 62 eyes of 36 control subjects. Superficial and deep retinal capillary vessel density (VD SVP and DVP) in the whole 3 × 3 mm macular and parafoveal area, foveal avascular zone (FAZ) area, and central retinal thickness (CRT) were measured using the AngioAnalytics software. The OCTA parameters were evaluated in both groups using a multivariate regression model, after controlling for the effect of imaging quality (SQ). RESULTS: There was no significant difference in age between the subjects with monoclonal gammopathy and the controls (63.59 ± 9.33 vs. 58.01 ± 11.46 years; p > 0.05). Taking into account the effect of image quality, the VD SVP was significantly lower in the MG group compared to the control group (44.54 ± 3.22% vs. 46.62 ± 2.84%; p < 0.05). No significant differences were found between the two groups regarding the other OCTA parameters (p > 0.05). CONCLUSIONS: A decreased superficial retinal capillary vessel density measured using OCTA in patients with MG suggests a slow blood flow, reduced capillary circulation, and consequent tissue hypoperfusion. An evaluation of retinal circulation using OCTA in cases of monoclonal gammopathy may be a sensitive method for the non-invasive detection and follow-up of early microcirculatory dysfunction caused by increased viscosity.

[Congenital aniridia patients' experience on their visual impairment in Hungary.] / Veleszületett aniridiás betegek látáskárosodással kapcsolatos tapasztalatai Magyarországon.

INTRODUCTION: Aniridia is a rare congenital panocular disease associated with varying degrees of visual acuity impairment. OBJECTIVE: To assess the experiences of congenital aniridia patients in Hungary, with visual impairment using a questionnaire developed by the ANIRIDIA-NET. PATIENTS AND METHOD: Patients completed the Hungarian version of the 20-item ANIRIDIA-NET questionnaire with our assistance. The questionnaire covered demographic data, the most common complaints caused by the disease, the difficulties caused by low vision in different life situations and the frequency of low vision aids used in daily life. RESULTS: 33 subjects (17 female [51.51%] and 16 male [48.48%]), 16 (48.5%) children and 17 (51.5%) adults completed the questionnaire, with an age of 25.69 ± 17.49 years (5-59 years). Daily photosensitivity was reported by 27 (81.8%), dry eyes by 5 (15.2%), tearing by 4 (12.1%), fluctuating vision by 3 (9.1%), and eye pain by 2 (6.1%) subjects. The majority of respondents said that personal communication with schoolmates (16 [48.5%]) or colleagues at work (11 [33.3%]) never caused difficulties because of their visual impairment. 29 people (87.9%) never needed help with daily routines at home, 24 (72.7%) with getting to school/work and 17 (51.5%) with various activities. 29 people (87.8%) never used low vision aids for communication, 23 (69.7%) for travelling, 20 (60.6%) for participating in social activities, 18 (54.5%) for studying/work. CONCLUSION: Although aniridia is associated with reduced visual acuity, the majority of people with congenital aniridia, especially in childhood, manage to cope with personal communication and various life situations without difficulty, despite their eye complaints. Low vision aids can be an important aid for them as they grow into adulthood and as they age. Orv Hetil. 2023; 164(34): 1342-1349.

[Staging of aniridia-associated keratopathy]. / Az aniridiához társult keratopathia stádiumbeosztása.

INTRODUCTION: Congenital aniridia is a rare panocular disease that affects almost all eye structures leading in most patients to reduced visual acuity. Ophthalmological signs include aniridia-associated keratopathy, secondary glaucoma, cataract, macular and optic nerve head hypoplasia, nystagmus. Although the term aniridia-associated keratopathy has long been used in the literature, various staging proposals have been described. OBJECTIVE: To analyze aniridia-associated keratopathy stages, using available literature classifications, in patients with aniridia in Hungary. PATIENTS AND METHODS: We examined 65 eyes of 33 patients with congenital aniridia (age: 25.69 ± 17.49 [5-59] years, 17 females [51.51%]). We recorded the corneal status by slit-lamp examination and classified the corneal abnormalities according to the Mackman, Mayer, López-García and Lagali staging. RESULTS: According to Mackman's classification, 8 eyes (12.3%) were in stage 0, 0 eye in stage 1A, 38 eyes (58.46%) in stage 1B and 19 eyes (29.23%) in stage 2. According to Mayer, stage I included 8 eyes (12.3%), stage II 38 eyes (58.46%), stage III 5 eyes (7.7%), stage IV 7 eyes (10.77%) and stage V 7 eyes (10.77%). In López-García's classification, 8 eyes (12.3%) could not be grouped, 20 eyes (30.77%) were in stage 1, 18 eyes (27.7%) in stage 2 and 19 eyes (29.3%) in stage 3. Lagali's classification included 8 eyes (12.3%) in stage 0, 20 eyes (30.77%) in stage 1, 18 eyes (27.7%) in stage 2, 5 eyes (7.7%) in stage 3 and 14 eyes (21.54%) in stage 4. CONCLUSION: We recommend using Lagali's staging scheme for aniridia-associated keratoptahy due to its ease of use, detailed progression assessment, and treatment planning. In stage 1 according to Lagali, blood vessels cross the limbus by up to 1 mm, in stage 2 the central 2-3 mm of the corneal area is spared of blood vessels. When the blood vessels reach the center of the cornea, it is stage 3, followed by opaque, uneven corneal pannus in stage 4. Orv Hetil. 2023; 164(27): 1063-1069.

[Congenital aniridia - Hungarian data of a spectrum disease]. / Congenitalis aniridia ­ egy spektrumbetegség magyarországi adatai.

INTRODUCTION: Congenital aniridia is a rare disease, characterised by the complete or partial absence of the iris, but lesions may be present in all structures of the eye. OBJECTIVE: To determine the prevalence of ocular diseases in congenital aniridia by analyzing patients from a Hungarian centre. PATIENTS AND METHODS: Patients at the Department of Ophthalmology of Semmelweis University, examined between October 2005 and May 2022, have been included. After taking the patients' medical history, a detailed ophthalmological examination has been performed. RESULTS: Of the 82 patients in the database, 33 (age 25.69 ± 17.49 [5-59] years, 17 females [51.51%]) presented for examination and 65 eyes were examined. Nystagmus was found in 45 eyes of 23 patients (69.23%), and the patients' uncorrected distance visual acuity was 0.14 ± 0.128 (0.9 logMAR; 0.63-0.005). The aniridia-associated keratopathy was Grade 0 in 8 eyes (12.3%), Grade 1 in 10 eyes (15.38%), Grade 2 in 16 eyes (24.62%), Grade 3 in 4 eyes (6.15%) and Grade 4 in 25 eyes (38.46%). 30 eyes (46.15%) of 15 patients had secondary glaucoma, 6 eyes (9.2%) of 3 patients were glaucoma suspect. 8 eyes (12.3%) had a clear lens, 44 eyes (67.69%) had cataract, of which 22 (33.84%) were anterior cortical polar cataracts. 13 eyes (20%) were pseudophakic (PCL) and 7 eyes (10.77%) had lens dislocation or zonular insufficiency. Macular hypoplasia was found in 6 eyes of 3 patients (4.6%) and optic nerve head malformation in 2 eyes of 1 patient (3.03%). CONCLUSION: The ocular signs of congenital aniridia are aniridia-associated keratopathy, secondary glaucoma, cataract, macular and optic nerve head hypoplasia. Systematic collaboration of different ophthalmological specialties is required for the management and care of all these ocular abnormalities. Orv Hetil. 2023; 164(4): 148-155.

["Cocaine eye syndrome"]. / "Kokainszem-szindróma".

Our aim is to summarize the effect of cocaine on the ocular surface, the so-called "cocaine eye syndrome" and to present a case report. Several factors are responsible for the development of an ophthalmic disease during cocaine consumption such as direct cytotoxicity of the drugs on corneal epithelial cells, damaged corneal innervation, ocular surface desiccation due to reduced blinking reflex, low-degree chemical burn of corneal epithelial cells and mechanical abrasion of the ocular surface. In our 25-year-old patient, there was deteriorated visual acuity and corneal erosion with corneal deposits of the right eye, directly following drug consumption, which could be healed through corneal abrasion by use of ethylenediaminetetraacetic acid (EDTA) and therapeutic contact lens. If an ophthalmic examination reveals abnormalities with characteristics of "cocaine eye syndrome" and no other corneal disease affecting corneal innervation can be verified, the suspicion of drug use should be taken into consideration. Timely appropriate treatment may eliminate complaints, restore visual acuity and improve quality of life. Orv Hetil. 2022; 163(47): 1886-1890.

Corneal Densitometry and In Vivo Confocal Microscopy in Patients with Monoclonal Gammopathy-Analysis of 130 Eyes of 65 Subjects.

BACKGROUND: Corneal imaging may support an early diagnosis of monoclonal gammopathy. The goal of our study was to analyze corneal stromal properties using Pentacam and in vivo confocal cornea microscopy (IVCM) in subjects with monoclonal gammopathy. PATIENTS AND METHODS: In our cross-sectional study, patients with monoclonal gammopathy (130 eyes of 65 patients (40.0% males; age 67.65 ± 9.74 years)) and randomly selected individuals of the same age group, without hematological disease (100 eyes of 50 control subjects (40.0% males; age 60.67 ± 15.06 years)) were included. Using Pentacam (Pentacam HR; Oculus GmbH, Wetzlar, Germany), corneal stromal light scattering values were obtained (1) centrally 0-2 mm zone; (2) 2-6 mm zone; (3) 6-10 mm zone; (4) 10-12 mm zone. Using IVCM with Heidelberg Retina Tomograph with Rostock Cornea Module (Heidelberg Engineering, Heidelberg, Germany), the density of hyperreflective keratocytes and the number of hyperreflective spikes per image were manually analyzed, in the stroma. RESULTS: In the first, second and third annular zone, light scattering was significantly higher in subjects with monoclonal gammopathy, than in controls (p ≤ 0.04). The number of hyperreflective keratocytes and hyperreflective spikes per image was significantly higher in stroma of subjects with monoclonal gammopathy (p ≤ 0.012). CONCLUSIONS: Our study confirms that increased corneal light scattering in the central 10 mm annular zone and increased keratocyte hyperreflectivity may give rise to suspicion of monoclonal gammopathy. As corneal light scattering is not increased at the limbal 10-12 mm annular zone in monoclonal gammopathy subjects, our spatial analysis provides evidence against the limbal origin of corneal paraprotein deposition. Using IVCM, stromal hyperreflective spikes may represent specific signs of monoclonal gammopathy.

Ocular signs and comorbidities in monoclonal gammopathy: Analysis of 84 eyes of 42 subjects / A monoklonális gammopathia szemészeti jelei és szövodményei: 42 beteg 84 szemének vizsgálata

Összefoglaló. Célkituzés: A monoklonális gammopathia szemészeti jeleinek és szövodményeinek vizsgálata. Betegek és módszerek: Két nagy budapesti hematológiai ellátóhely 1999 és 2020 között diagnosztizált és/vagy kezelt, monoklonális gammopathiát mutató betegeit vizsgáltuk (42 beteg 84 szeme, 42,86% férfi; átlagéletkor 63,83 ± 10,76 év). A hematológiai diagnózis 3 esetben bizonytalan jelentoségu monoklonális gammopathia, 34 esetben myeloma multiplex, 3 esetben parázsló myeloma, 1-1 esetben Waldenström-macroglobulinaemia és amyloidosis voltak. Kontrollcsoportként véletlenszeruen kiválasztott, hasonló korcsoportú, hematológiai betegség nélküli egyéneket vizsgáltunk (43 beteg 86 szeme, 32,56% férfi; átlagéletkor 62,44 ± 11,89 év). A szemészeti vizsgálat elott minden személy kitöltötte a Szemfelszíni Betegség Index (OSDI-) kérdoívet. A szemészeti vizsgálat során a látóélesség vizsgálata mellett pupillatágítást követoen réslámpás vizsgálatot végeztünk. Eredmények: Monoklonális gammopathiában az OSDI-érték szignifikánsan magasabb volt, mint a kontrollokban (p = 0,002). Gammopathiában 3 beteg 5 szeménél (5,95%) találtunk potenciális szaruhártya-immunglobulinlerakódást. Gammopathiában szárazszem-betegség 66,67%-ban, szürke hályog 55,95%-ban, Meibom-mirigy-diszfunkció 20,24%-ban, hátsó kérgi szürke hályog 19,05%-ban, egyéb szaruhártyahegek és -homályok 17,86%-ban, krónikus szemhéjgyulladás 14,29%-ban, szemészeti eltérés hiánya 11,90%-ban, macula- és/vagy retinadrusen 9,52%-ban, szaruhártya-immunglobulinlerakódás 5,95%-ban, epiretinalis membrán 5,95%-ban, korábbi szürkehályog-mutét 5,95%-ban, glaucoma 4,76%-ban, Fuchs-dystrophia 2,38%-ban, perifériás retinadegeneráció 2,38%-ban, chorioidea naevus 2,38%-ban, diabeteses retinopathia 1,19%-ban, arteria centralis retinae elzáródás 1,19%-ban, vena centralis retinae ágelzáródás 1,19%-ban, amblyopia 1,19%-ban volt kimutatható. A szárazszem-betegség (p = 0,002), a hátsó kérgi szürke hályog (p = 0,001), a szürke hályog (p<0,00001) és az egyéb szaruhártyahegek és -homályok (p = 0,01) szignifikánsan magasabb arányban fordultak elo a monoklonális gammopathiát mutató betegekben, mint a kontrollokban. Következtetés : Monoklonális gammopathiában a szárazszem-betegség és a szürke hályog a leggyakoribb szemészeti eltérés. A monoklonális gammopathia potenciális szemészeti jelei és szövodményei miatt javasoljuk a betegek évenkénti szemészeti ellenorzését, életminoségük javítása érdekében. Orv Hetil. 2021; 162(38): 1533-1540. OBJECTIVE: To examine ocular signs and ocular comorbidities in monoclonal gammopathy. PATIENTS AND METHODS: We analyzed patients from two large referral hematology centers in Budapest, who were diagnosed and/or treated with monoclonal gammopathy between 1997 and 2020 (84 eyes of 42 patients, 42.86% male, mean age 63.83 ± 10.76 years). Before the ophthalmic examination, the subjects filled in the Ocular Surface Disease Index (OSDI) questionnaire. Ophthalmic examination included visual acuity test and slit-lamp examination following dilation of the pupil. RESULTS: OSDI scores were significantly higher in subjects with monoclonal gammopathy than in controls (p = 0.002). Among gammopathy subjects, we observed potential corneal immunoglobulin deposition in 5 eyes of 3 patients (5.95%). In gammopathy subjects, there was dry eye disease (66.67%), cataract (55.95%), Meibomian gland dysfunction (20.24%), posterior cortical cataract (19.05%), corneal scars and degenerations (17.86%), chronic blepharitis (14.29%), absence of ocular complaint (11.90%), macular or retinal drusen (9.52%), corneal immunoglobulin deposition (5.95%), epiretinal membrane (5.95%), previous cataract surgery (5.95%), glaucoma (4.76%), Fuchs dystrophy (2.38%), peripheral retinal degeneration (2.38%), chorioideal naevus (2.38%), diabetic retinopathy (1.19%), central retinal artery occlusion (1.19%), central retinal vein branch occlusion (1.19%) and amblyopia (1.19%). The proportion of dry eye disease (p = 0.002), posterior cortical cataract (p = 0.001), cataract (p<0.00001), and corneal scars and degenerations (p = 0.01) were significantly higher in gammopathy subjects than in controls. CONCLUSION: Dry eye disease and cataracts are the most common ocular comorbidities in patients with monoclonal gammopathy. Therefore, due to the potential ocular signs and comorbidities of monoclonal gammopathy, we suggest a regular, yearly ophthalmic checkup of these patients to improve their quality of life. Orv Hetil. 2021; 162(38): 1533-1540.

Ocular Signs and Ocular Comorbidities in Monoclonal Gammopathy: Analysis of 80 Subjects.

PURPOSE: To examine the ocular signs of monoclonal gammopathy and to evaluate ocular comorbidities in subjects with monoclonal gammopathy. Patients and Methods. We analyzed patients from two large referral hematology centers in Budapest, diagnosed and/or treated with monoclonal gammopathy between 1997 and 2020. As a control group, randomly selected individuals of the same age group, without hematological disease, have been included. There were 160 eyes of 80 patients (38.75% males; age 67.61 ± 10.48 (range: 38-85) years) with monoclonal gammopathy and 86 eyes of 43 control subjects (32.56% males; age 62.44 ± 11.89 (range 37-86) years). The hematological diagnosis was MGUS in 9 (11.25%), multiple myeloma in 61 (76.25%), smoldering myeloma in 6 (7.50%), and amyloidosis or Waldenström macroglobulinemia in 2 cases (2.50%-2.50%). Before detailed ophthalmic examination with fundoscopy, 42 subjects with gammopathy (52.50%) and all controls filled the Ocular Surface Disease Index (OSDI) questionnaire. RESULTS: The OSDI score and best-corrected visual acuity (BCVA) were significantly worse in subjects with monoclonal gammopathy than in controls (p=0.02; p=0.0005). Among gammopathy subjects, we observed potential corneal immunoglobulin deposition in 6 eyes of 4 (3.75%) patients. Ocular surface disease (p=0.0001), posterior cortical cataract (p=0.01), and cataract (p=0.0001) were significantly more common among gammopathy subjects than in controls (χ 2 test). CONCLUSIONS: Ocular surface disease and cataract are more common, and BCVA is worse in patients with monoclonal gammopathy than in age-matched controls. Therefore, and due to the potential ocular signs and comorbidities of monoclonal gammopathy, we suggest a regular, yearly ophthalmic checkup of these patients to improve their quality of life.

Graft survival using cadaver and multiorgan donors between 2008 and 2017 in our department / Cadaverbol és multiorgan donorból származó szaruhártyák túlélése 2008 és 2017 között klinikánkon.

Összefoglaló. Bevezetés: Az elso szaruhártya-bank 1944-es alapítása óta jelentos változásokon ment át. A szaruhártya túlélését számos tényezo befolyásolja, így a tárolási mód, melynek a szövet lejárati ideje szerint rövid, közép és hosszú távú módszereit fejlesztették ki. Célkituzés: Retrospektív vizsgálatunk célja a 2008. január 1. és 2017. december 31. között perforáló és lamelláris keratoplasztika során felhasznált cadaverbol és multiorgan donorból származó szaruhártyák túlélésének vizsgálata volt a Semmelweis Egyetem Szemészeti Klinikáján. Módszer: Feljegyeztük a recipiens nemét, életkorát, a mutétet indikáló klinikai diagnózist, a mutét idopontját, a szövettani vizsgálat eredményét, valamint, hogy a beültetett szaruhártya cadaverbol vagy multiorgan donorból származott. Meghatároztuk, hogy a recipiens életkora korrelált-e a rekeratoplasztikáig eltelt idovel. Eredmények: 1451 szaruhártya-átültetés történt 1088 beteg (44,6% férfi) 1159 szemén (életkor 62,8 ± 18,5 év), melyek között 938 (64,6%) cadaver és 262 (18,0%) multiorgan donor került felhasználásra, 251 esetben (17,2%) nem állt rendelkezésre adat. A leggyakoribb primer diagnózis a szaruhártya-dekompenzáció volt (325 eset, 28%). A primer keratoplasztikák során felhasznált szaruhártyák 740 esetben (63,8%) cadaverbol, 212 esetben (18,2%) multiorgan donorból származtak, 207 esetben (17,8%) nem állt rendelkezésre adat. Elso rekeratoplasztika a primer keratoplasztikák közül 217 esetben (18,7%) történt. A leggyakoribb szövettani diagnózis az endothelsejt-degeneráció volt (130 esetben, 60,4%). 146 esetben (67,2%) korábban cadaver, 31 esetben (14,2%) multiorgan donor esetén került sor ismételt mutétre, 40 esetben (18,4%) nem állt rendelkezésre adat. Következtetés: Klinikánkon elsosorban cadaverbol származó donorok biztosítják a szaruhártya átültetésekhez szükséges szövetet. Cadaverbol vagy multiorgan donorból származó szaruhártyák esetén nem kerül gyakrabban sor rekeratoplasztikára. A szaruhártya-banki tevékenység további fejlesztésével növelheto a donorok túlélése hazánkban. Orv Hetil. 2021; 162(13): 488-496. INTRODUCTION: Corneal banking methods have been changing since the foundation of the first corneal bank in 1944. Corneal graft survival may be affected by several factors, among others the storage method, which may be short-, middle- and long-term storage. OBJECTIVE: To investigate corneal graft survival at the Department of Ophthalmology, Semmelweis University between 1 January 2008 and 31 December 2017, using cadaver and multiorgan donors for penetrating and lamellar keratoplasty, retrospectively. METHOD: Recipient sex, age, clinical diagnosis, date of surgery, histological examination results and origin of donors (cadaver or multiorgan donor) were recorded. Correlation between recipient age and time to repeat keratoplasty was also analyzed. RESULTS: There were 1451 keratoplasties in 1159 eyes (age 62.8 ± 18.5 years) of 1088 patients (44.6% male) using 938 (64.6%) cadaver and 262 (18.0%) multiorgan donors, data was not available in 251 (17.2%) cases. There was repeat keratoplasty in 217 patients (18.7% of first keratoplasties). The most common histological diagnosis was endothelial decompensation (130 cases, 60.4%) in these cases. In patients with a first repeat keratoplasty, in 146 cases (67.2%) the first donor originated from cadavers, in 31 cases (14.2%) from multiorgan donors and in 40 cases (18.4%) data were not available. CONCLUSION: Corneal donors mainly originate from cadavers at our Department. The necessity of repeat keratoplasties does not differ using cadaver or multiorgan donors. With further development of corneal banking, donor survival may be increased in Hungary. Orv Hetil. 2021; 162(13): 488-496.

Expression and properties of the highly alkalophilic phenylalanine ammonia-lyase of thermophilic Rubrobacter xylanophilus.

The sequence of a phenylalanine ammonia-lyase (PAL; EC: 4.3.1.24) of the thermophilic and radiotolerant bacterium Rubrobacter xylanophilus (RxPAL) was identified by screening the genomes of bacteria for members of the phenylalanine ammonia-lyase family. A synthetic gene encoding the RxPAL protein was cloned and overexpressed in Escherichia coli TOP 10 in a soluble form with an N-terminal His6-tag and the recombinant RxPAL protein was purified by Ni-NTA affinity chromatography. The activity assay of RxPAL with l-phenylalanine at various pH values exhibited a local maximum at pH 8.5 and a global maximum at pH 11.5. Circular dichroism (CD) studies showed that RxPAL is associated with an extensive α-helical character (far UV CD) and two distinctive near-UV CD peaks. These structural characteristics were well preserved up to pH 11.0. The extremely high pH optimum of RxPAL can be rationalized by a three-dimensional homology model indicating possible disulfide bridges, extensive salt-bridge formation and an excess of negative electrostatic potential on the surface. Due to these properties, RxPAL may be a candidate as biocatalyst in synthetic biotransformations leading to unnatural l- or d-amino acids or as therapeutic enzyme in treatment of phenylketonuria or leukemia.

Preparation of unnatural amino acids with ammonia-lyases and 2,3-aminomutases.

Ammonia-lyases catalyze a wide range of processes leading to α,ß-unsaturated compounds by elimination of ammonia. In this chapter, ammonia-lyases are reviewed with major emphasis on their synthetic applications in stereoselective preparation of unnatural amino acids. Besides the synthesis of various unnatural α-amino acids with the aid of phenylalanine ammonia-lyases (PALs) utilizing the 3,5-dihydro-5-methylidene-4H-imidazol-4-one (MIO) prosthetic groups, the biotransformations leading to various unnatural ß-amino acids with phenylalanine 2,3-aminomutases using the same catalytic MIO prosthetic group are discussed. Cloning, production, purification, and biotransformation protocols for PAL are described in detail.