Preparation, properties and metabolism of retro-3-dehydroretinyl acetate.
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ABSTRACT:
SUBMITTER: Mallia AK
PROVIDER: S-EPMC1186787 | biostudies-other | 1968 Sep
REPOSITORIES: biostudies-other
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Project description:1. retro-Retinyl acetate was shown to exert its biological activity by conversion into vitamin A. 2. When administered orally, retro-retinyl acetate was hydrolysed to retro-retinol in the intestine, isomerized to retinol and esterified before being transported to the liver for storage. 3. Administration of the compound at as high a dose as 4.0mg./day for 4 days led to the accumulation of both vitamin A and retro-vitamin A in the liver. The amount of retro-vitamin A in liver gradually decreased until it was almost completely converted into vitamin A in 18 days. 4. Intraperitoneal administration of the compound led to the accumulation of both vitamin A and retro-vitamin A in liver and other tissues. No vitamin A was detected in any tissue of rats receiving retro-retinyl acetate intraperitoneally after enterectomy. 5. The small intestine is the major site of conversion of retro-vitamin A into vitamin A. The conversion could also be demonstrated by everted intestinal sacs. 6. The biological potency of retro-retinyl acetate determined by the rat-growth assay was 20.5% that of all-trans-retinyl acetate, when given orally.
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Project description:1. Methyl retinoate has been converted into methyl 5,6-monoepoxyretinoate by reaction with monoperphthalic acid. The epoxy acid ester on alkaline hydrolysis gave 5,6-monoepoxyretinoic acid. 2. Treatment of the 5,6-monoepoxy compounds with ethanolic hydrochloric acid gave the corresponding 5,8-epoxy (furanoid) compounds. 3. With lithium aluminium hydride, the acid and the ester groups were selectively reduced to primary alcohols. 4. Administration of methyl 5,6-monoepoxyretinoate intraperitoneally and subcutaneously had good growth response in vitamin A-deficient rats. 5. 5,6-Monoepoxyretinoic acid, when given intraperitoneally as the sodium salt, was 157% as active as all-trans-retinyl acetate. 6. Methyl 5,6-monoepoxyretinoate was hydrolysed to the epoxy acid by rat-liver homogenate. It had 35% of the biological activity of all-trans-retinyl acetate in the rat when given orally.
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Project description:Acetate kinase (ACK) (EC no: 2.7.2.1) interconverts acetyl-phosphate and acetate to either catabolize or synthesize acetyl-CoA dependent on the metabolic requirement. Among all ACK entries available in UniProt, we found that around 45% are multiple ACKs in some organisms including more than 300 species but surprisingly, little work has been done to clarify whether this has any significance. In an attempt to gain further insight we have studied the two ACKs (AckA1, AckA2) encoded by two neighboring genes conserved in Lactococcus lactis (L. lactis) by analyzing protein sequences, characterizing transcription structure, determining enzyme characteristics and effect on growth physiology. The results show that the two ACKs are most likely individually transcribed. AckA1 has a much higher turnover number and AckA2 has a much higher affinity for acetate in vitro. Consistently, growth experiments of mutant strains reveal that AckA1 has a higher capacity for acetate production which allows faster growth in an environment with high acetate concentration. Meanwhile, AckA2 is important for fast acetate-dependent growth at low concentration of acetate. The results demonstrate that the two ACKs have complementary physiological roles in L. lactis to maintain a robust acetate metabolism for fast growth at different extracellular acetate concentrations. The existence of ACK isozymes may reflect a common evolutionary strategy in bacteria in an environment with varying concentrations of acetate.
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