Preliminary studies of monoterpenoid variability in Satureja douglasii

Monoterpenoid composition of samples from 10 populations of Satureja douglasii in a 250-ha area were analyzed in Spring 1974. Two distinct compositional types were found: Type A contained large amounts of limonene and carvone but very small quantites of piperitenone, piperitone, pulegone and isomenthone (3-oxy compounds), whereas Type B was essentially the reverse. This variation is attributed to a genotypic difference. The amounts of 3-oxy compounds varied greatly among the Type B populations. Increasing shade conditions were correlated with increased amounts of the more reduced compounds isomenthone and piperitone. Clonal lines were established from two Type B populations whose habitats represented extremes of sun and shade conditions. The two clonal lines, which had very different compositions in the field, produced similar oils under controlled conditions. Growth under different temperature regimes had little effect on composition. Developmental changes in composition implied the precursor-product relationships piperitenone→piperitone and pulegone→isomenthone. The data suggest that S douglasii monoterpenoid compositional patterns are significantly influenced by genetic and environmental factors (probably light intensity) as well as developmental processes.     

Retinol oxidation to retinoic acid in human thyroid glandular cells

Abstract

Retinoic acid is regarded as the retinol metabolite that controls proliferation and differentiation of epithelial cells. In the present study, we investigated the potential role of xanthine dehydrogenase (XDH) in retinoic acid biosynthesis in human thyroid glandular cells (HTGC). In particular, we observed that cellular retinoids binding proteins (CRBPs) are also implicated in the biosynthetic pathway leading to retinoic acid formation in primary cultures of HTGC, as we have already reported for human mammary epithelial cells (HMEC). After partial protein purification, the enzyme responsible for retinoic acid biosynthesis was identified and quantified as XDH by immunoassay, by its ability to oxidize xanthine to uric acid and its sensitivity to the inhibitory effect of oxypurinol. The evidence of XDH-driven formation of retinoic acid in HTGC cultures further corroborates the potential role of XDH in retinoic acid biosynthesis in the epithelia.     

Regulation of endomembrane biogenesis in arabidopsis by phospatidic acid hydrolase

Coordination of membrane lipid biosynthesis is important for cell function during plant growth and development. Here we summarize our recent work on PHOSPHATIDIC ACID PHOSPHOHYDROLASE (PAH) which suggests that this enzyme is a key regulator of phosphaticylcholine (PC) biosynthesis in Arabidopsis thaliana. Disruption of PAH activity elevates phosphatidic acid (PA) levels and stimulates PC biosynthesis and biogenesis of the endoplasmic reticulum (ER). Furthermore, the activity of PHOSPHOCHOLINE CYTIDYLYLTRANSFERASE (CCT), which is the key enzyme controlling the rate of PC biosynthesis, is directly stimulated by PA and expression of a constitutively active version of CCT replicates the effects of PAH disruption. Hence PAH activity can control the abundance of PA, which in turn can modulate CCT activity to govern the rate of PC biosynthesis. Crucially it is not yet clear how PAH activity is regulated in Arabidopsis but there is evidence that PAH1 and PAH2 are both phosphorylated and further work will be required to investigate whether this is functionally significant.     

Enzymes of ammonia assimilation in legume nodules: A comparison between ureide- and amide-transporting plants

Levels of amide and ureide biogenic enzymes were compared in the plant cytosol fractions of root nodules from soybean ( Glycine max L. Merr., cv. Williams), pintobean ( Phaseolus vulgaris L. cv. Pinto) and Lupin ( Lupinus angustifolius L. cv. Frost). Enzymes of purine oxidation were found to be present in significant quantities only in ureide-transporting pintobean and soybean nodules. The levels of these enzymes were low in lupin, but this amide-exporter had significantly higher levels of asparagine synthetase. Enzymes of de novo purine biosynthesis and glycine biosynthesis were present at higher levels in pintobean and soybean, consistent with a role for de novo purine biosynthesis in ureide biogenesis. The low levels of these enzymes in lupin are consistent with a role in general purine and amino acid metabolism in these nodules, not directly related to the synthesis of transport compounds for fixed atmospheric nitrogen. Amino acid concentrations in soybean, pintobean and lupin nodules reflected the metabolic differences between amide and ureide plants. The comparative data presented are consistent with a pathway of ureide biogenesis using glutamine, glutamate and aspartate synthesized via reactions catalyzed by glutamine synthetase, glutamate synthase and aspartate aminotransferase in the de novo synthesis of purines followed by oxidation of these purines to produce the ureides allantoin and allantoic acid.     

Establishing microbial co‐cultures for 3‐hydroxybenzoic acid biosynthesis on glycerol

Converting renewable feedstocks to aromatic compounds using engineered microbes offers a robust approach for sustainable, environment‐friendly, and cost‐effective production of these value‐added products without the reliance on petroleum. In this study, rationally designed E. coli–E. coli co‐culture systems were established for converting glycerol to 3‐hydroxybenzoic acid (3HB). Specifically, the 3HB pathway was modularized and accommodated by two metabolically engineered E. coli strains. The co‐culture biosynthesis was optimized by using different cultivation temperatures, varying the inoculum ratio between the co‐culture strains, recruitment of a key pathway intermediate transporter, strengthening the critical pathway enzyme expression, and adjusting the timing for inducing pathway gene expression. Compared with the E. coli mono‐culture, the optimized co‐culture showed 5.3‐fold improvement for 3HB biosynthesis. This study demonstrated the applicability of modular co‐culture engineering for addressing the challenges of aromatic compound biosynthesis.     

谷氨酸棒状杆菌异源合成萜类化合物的研究进展

萜类化合物具有可观的商业价值,但生产过程复杂,产量低,利用微生物异源合成萜类化合物已成为热点。谷氨酸棒状杆菌内含合成萜类色素的途径,具有异源合成萜类化合物的天然优势和研究前景。首次对谷氨酸棒状杆菌合成萜类化合物进行了综述,从萜类合成途径、关键酶和全局调控机制三个方面进行了途经介绍。概述了谷氨酸棒状杆菌中单萜、倍半萜、四萜类化合物的异源合成,并对利用谷氨酸棒状杆菌高效合成萜类化合物所需解决的问题进行讨论,为谷氨酸棒状杆菌高效合成萜类化合物提供建议。     

Mechanisms of the anterograde trafficking of GPCRs: Regulation of AT1R transport by interacting proteins and motifs

Anterograde cell surface transport of nascent G protein‐coupled receptors (GPCRs) en route from the endoplasmic reticulum (ER) through the Golgi apparatus represents a crucial checkpoint to control the amount of the receptors at the functional destination and the strength of receptor activation‐elicited cellular responses. However, as compared with extensively studied internalization and recycling processes, the molecular mechanisms of cell surface trafficking of GPCRs are relatively less defined. Here, we will review the current advances in understanding the ER‐Golgi‐cell surface transport of GPCRs and use angiotensin II type 1 receptor as a representative GPCR to discuss emerging roles of receptor‐interacting proteins and specific motifs embedded within the receptors in controlling the forward traffic of GPCRs along the biosynthetic pathway.