Hydroxy(phenyl)pyruvic acid reductase in Actaea racemosa L.: a putative enzyme in cimicifugic and fukinolic acid biosynthesis.

MAIN CONCLUSION: Hydroxy(phenyl)pyruvic acid reductase from Actaea racemosa catalyzes dual reactions in reducing 4-hydroxyphenylpyruvic acid as well as ß-hydroxypyruvic acid. It thus qualifies to be part of fukinolic and cimicifugic acid biosynthesis and also photorespiration. The accumulation of fukinolic acid and cimicifugic acids is mainly restricted to Actaea racemosa (Ranunculaceae) and other species of the genus Actaea/Cimicifuga. Cimicifugic and fukinolic acids are composed of a hydroxycinnamic acid part esterified with a benzyltartaric acid moiety. The biosynthesis of the latter is unclear. We isolated cDNA encoding a hydroxy(phenyl)pyruvic acid reductase (GenBank OR393286) from suspension-cultured material of A. racemosa (ArH(P)PR) and expressed it in E. coli for protein production. The heterologously synthesized enzyme had a mass of 36.51 kDa and catalyzed the NAD(P)H-dependent reduction of 4-hydroxyphenylpyruvic acid to 4-hydroxyphenyllactic acid or ß-hydroxypyruvic acid to glyceric acid, respectively. The optimal temperature was at 38 °C and the pH optimum at pH 7.5. NADPH is the preferred cosubstrate (Km 23 ± 4 µM). Several substrates are accepted by ArH(P)PR with ß-hydroxypyruvic acid (Km 0.26 ± 0.12 mM) followed by 4-hydroxyphenylpyruvic acid (Km 1.13 ± 0.12 mM) as the best ones. Thus, ArH(P)PR has properties of ß-hydroxypyruvic acid reductase (involved in photorespiration) as well as hydroxyphenylpyruvic acid reductase (possibly involved in benzyltartaric acid formation).

Pseudophakic retinal detachment after uneventful phacoemulsification and subsequent neodymium: YAG capsulotomy for capsule opacification.

PURPOSE: To determine the incidence of retinal detachment (RD) after neodymium:YAG (Nd:YAG) laser capsulotomy for posterior capsule opacification (PCO) and define the characteristics of this type of RD. SETTING: A private practice, with statistical evaluation at a university department. METHODS: Five hundred twenty-six consecutive eyes that had Nd:YAG capsulotomy because of visually disturbing PCO were followed prospectively for up to 52 months (median 21 months) to determine the incidence of RD. The median age of the 142 men and 320 women was 76 years and the median axial length, 23.3 mm (range 20.5 to 31.3 mm). Before the capsulotomy, all eyes had uneventful phacoemulsification with implantation of a posterior chamber intraocular lens (PC IOL). Eyes with additional surgical procedures or with panretinal laser photocoagulation were excluded. Eyes in which a retinal hole had been treated before Nd:YAG (n = 4) were included. The fundus was examined by binocular indirect ophthalmoscopy with a 2.2 diopter Volk lens in full mydriasis. If necessary, an examination with a 3-mirror lens was done. RESULTS: The incidence of RD was 0% (0/483; 95% confidence interval [CI], 0.0%-0.8%) at 6 months, 0% (0/407; 95% CI, 0.0%-0.9%) at 12 months, and 0.5% (1/213; 95% CI, 0.0%-2.6%) at 24 months. Twenty-one months after Nd:YAG capsulotomy, 1 eye developed an RD that occurred as the result of a horseshoe tear that reopened. The tear, which formed 7 months after phacoemulsification and PC IOL implantation and 6 years before Nd:YAG capsulotomy, had been immediately treated with argon laser photocoagulation. Excluding the 4 eyes with preexisting tears, presumably sealed retinal holes, the incidence at 24 months was 0% (0/212; 95% CI, 0.0%-1.7%). No other eye developed RD over the follow-up. CONCLUSIONS: Retinal detachment after Nd:YAG capsulotomy for PCO was rare in eyes that had previous uneventful phacoemulsification and PC IOL implantation. The exact relationship between the 2 events remains to be established.