Adaptation of the electron transport chain improves the biocatalytic efficiency of progesterone 17α hydroxylation / 生物工程学报

17α hydroxylase is a key enzyme for the conversion of progesterone to prepare various progestational drug intermediates. To improve the specific hydroxylation capability of this enzyme in steroid biocatalysis, the CYP260A1 derived from cellulose-mucilaginous bacteria Sorangium cellulosum Soce56 and the Fpr and bovine adrenal-derived Adx4-108 derived from Escherichia coli str. K-12 were used to construct a new electron transfer system for the conversion of progesterone. Selective mutation of CYP260A1 resulted in a mutant S276I with significantly enhanced 17α hydroxylase activity, and the yield of 17α-OH progesterone reached 58% after optimization of the catalytic system in vitro. In addition, the effect of phosphorylation of the ferredoxin Adx4-108 on 17α hydroxyl activity was evaluated using a targeted mutation technique, and the results showed that the mutation Adx4-108T69E transferred electrons to S276I more efficiently, which further enhanced the catalytic specificity in the C17 position of progesterone, and the yield of 17α-OH progesterone was eventually increased to 74%. This study provides a new option for the production of 17α-OH progesterone by specific transformation of bacterial-derived 17α hydroxylase, and lays a theoretical foundation for the industrial production of progesterone analogs using biotransformation method.

Changes in Somatostatin Receptor mRNA Levels by G Protein Mutation in GH3 Cells Which Show Responsiveness to Growth Hormone-Releasing Hormone / 대한내분비학회지

BACKGROUNDS: GH3 cells lack growth hormone(GH)-releasing hormone(GHRH) receptors. In this study, GH3 cells permanently transfected with human GHRH receptor cDNA(GH3-GHRHR cells), were established in order to examine the effects of GHRH and G protein mutation(gsp oncogene) on the levels of somatostatin receptor mRNA. METHODS: GH3 cells were permanently transfected with a plasmid expressing human GHRH receptor cDNA. The GHRH receptor mRNA was detected by RT-PCR. The responsiveness to GHRH was evaluated using a GHRH binding assay, Western blot analysis, Northern blot analysis, and measurements of the intracellular cAMP levels and GH release. Cells were transiently transfected with the gsp oncogene, and then treated with GHRH or octreotide for 4h. The sst1 and sst2 mRNA levels were measured using real-time RT-PCR analyses. RESULTS: GHRH receptor mRNA was detected in the GH3 cells permanently transfected with human GHRH receptor cDNA. The GHRH binding assay showed that GHRH was bound to the GH3-GHRHR cells. The GHRH treatment increased the intracellular cAMP levels, GH release, GH mRNA levels, and MAPK activity, as well as the levels of sst1 and sst2 mRNA. Transient expression of the gsp oncogene for 48h increased the cAMP, GH release, and levels of sst1 and sst2 mRNA. In the gsp-transfected GH3-GHRHR cells, GHRH stimulation resulted in decreases in the magnitude of the increase in the levels of sst1 and sst2 mRNA compared to those transfected with a control vector. Octreotide treatment did not alter the levels of sst1 and sst2 mRNA in either the control or gsp-transfected cells. CONCLUSION: These results suggest that GH3 cells permanently transfected with the GHRH receptor are useful in the in vitro studies on the actions of GHRH. The gsp oncogene was shown to increases the levels of sst1 and sst2 mRNA in GH3 cells, but these findings are unlikely to be the major mechanism by which gsp-positive pituitary tumors show a greater response to somatostatin. The discrepancy between the in vivo and these in vitro results should be examined further.

Relationship between the Expression of Growth Hormone-Releasing Hormone Receptor Gene and Endocrinologic Profiles in GH-Secreting Pituitary Adenomas / 대한내분비학회지

BACKGROUND: Growth hormone-releasing hormone (GHRH) plays a key role in the regulation of the proliferation and differentiation of somatomammotroph cells as well as secretion of GH. The actions of GHRH are mediated through the GHRH receptor (GHRH-R) that is a G protein coupled receptor with seven transmembrane domains. It has been demonstrated that alternative splicing occurs in the third cytoplasmic domain of rat and human GHRH-R mRNA, However, the clinical significance of the altemative splicing remains to be unsolved. To find an insight into the clinical significance, we investigate the correlation between the GHRH-R gene expression and a variety of clinical clinical and endocrinological findings in 11 acromegalic patients. METHODS: Eleven acromegalic patients (3 males and 8 females, mean age 43.5 years) were included in this study. Six endocrine tests were carried out to evaluate the GH seeretory function of tumors. Invasiveness of tumors were evaluated by preoperative MRI findings on the basis of Hardys classification. Sequence the gsp oncogene and estimate the GHRH-R gene expression by RT-PCR and in vitro transcription. RESULTS: Three different sized cDNA fragments, 250 bp, 700 bp and 810 bp, were found after RT-PCR. The amount of 250 bp fragment was higher than those of the other two fragments. The clinical findings (age, size, GH level, frequency of paradoxical response to TRH or GnRH, octreotide response, hypothalamic somatostatinergic activity) of the group with high expression of the 250 bp fragment did not significantly differ from those of the group with low expression. The GHRH-R gene expression of tumors with gsp oncogene did not significantly differ from that of tumors without gsp oncogene. CONCLUSION: These results suggest that the expression of GHRH-R gene may not be an important determinant for tumor growth, and the lower GH response to GHRH of tumors with gsp oncogene may not be attributed to the lower expression of GHRH-R gene. The expression of GHRH-R is likely to be regulated by a certain property of tumors for GH secretion and growth.

Gene Expression of Somatostatin Receptor Subtype 2 and 5 in GH-Secreting Pituitary Adenomas / 대한내분비학회지

BACKGROUND: SSTR2 and SSTR5 are most frequently observed in GH-secreting pituitary tumors, and SSTR5 is believed to be more specific to mammosomatotroph lineage. Octreotide binds with high affinity to those two types. There is no report that investigates the quantitative comparison of the two subtype gene expressions, and the correlation between their gene expressions and GH response to octreotide in GH-secreting pituitary adenomas. METHOD: GH response to octreotide was examined in 8 acromegalic patients before transsphenoidal adenomectomy. Genomic DNA and RNA were prepared from fresh frozen tumor tissues. PCR was performed to amplify and sequence the region between codon 184 and 251 that includes exons 8 and 9 of the Gas gene. mRNAs of SSTR2 and SSTRS were quantitated by the comparative RT-PCR and in vitro transcription. RESULTS: The in vitro transcripts of SSTR2 and SSTR5 cDNA were detected in all tumors. The amount of SSTR transcripts was considerably variable between the tumors. The amount of SSTR5 transcript was significantly smaller than that of SSTR2 transcript (0.07+-0.02 vs. 0.87+-0.10), and they did not show any correlation . There was no signicant difference in sex, age, tumor size and grade, basal GH levels, and the GH responses to octreotide between the group with high and low SSTR gene expression. No significant correlation was found between the GH response to octreotide and the amount of SSTR2 transcript, wherease the amount of SSTR5 transcripts showed a tendency of negative correlation with the octreotide response. Tumors with gsp oncogene showed significantly higher response to octreotide than those without the oncogene. The amount of SSTRS transcript in gsp-positive tumors was significantly smaller than in gsp-negative tumors (0.03+-0.01 vs. 0.12+-0.03). CONCLUSION: These results suggest that SSTRS gene expression is lower than that of SSTR2 in GH-secreting adenomas. It is probably attributed to the binding of somatostatin to SSTR5 which has a higher affinity to the hypothalamic somatostatin, Tumors with gsp-oncogene is likely to express a higher density of SSTR5 than those without the oncogene.

Effect of Fusion Protein Cleavage Site Mutations of NDV ZJ1 Strain on Its Fusion Activity / 微生物学通报

NDV strain ZJ1 strain , a highly virulent NDV strain, has been prevalent among the waterfowls in China mainland in the past years. Multi-basic amino acid sequence distribute in the protease cleavage site of F protein of this strain. Recombinant expressing plasmid pCI-FT, was generated by converting multi-basic amino acid sequence of 112, 115, 117 of the protease cleavage site of F_ 0 protein, to the non-basic amino acid sequence characteristic of avirulent NDV strain. The result from co-expression of mutant or parental F protein with homologous HN protein in COS-1 cells revealed that both mutant and parental F protein had fusion activity. The result from co-expression of mutant or parental F protein with homologous HN protein in CEF cells showed that the cleavage activity of mutant F protein was significantly reduced. The study built a foundation for mutagenesis of amino acid sequence of the protease cleavage site of F_ 0 protein at the full-length cDNA clone level, study on factors contributing to virulence and construction of candidate vaccine strain, and so on.