Carbomycin B

A 3.2-kb DNA fragment of the carbomycin biosynthetic region including the 3-O-acyltransferase gene (acyA) from Streptomyces thermotolerans was sequenced, and four ORFs were found in the fragment. The second ORF, designated ORF-A, was transcribed in the opposite direction to the other three ORFs. The first ORF was identified as carA, a gene for carbomycin resistance. The amino acid sequence of ORF-A was homologous to proteins of the cytochrome P-450 family. Streptomyces lividans transformed with pCB20, in which ORF-A was subcloned, epoxidized carbomycin B at its C-12, 13 positions, thus producing carbomycin A. The third ORF, the amino acid sequence of which showed a homology to macrolide antibiotics O-acyltransferases was identified as acyA. The last ORF (ORF-B), which starts just 3 bp downstream from the TGA termination codon of acyA, was thought to be a carbomycin 4-O-methyltransferase gene, because the amino acid sequence deduced from ORF-B showed high homology to a putative midecamycin 4-O-methyltransferase encoded on mdmC.

Objective: To explore the effect difference between the skin needle embedding therapy and western medication for obese impaired glucose tolerance (IGT). Methods: A total of 300 cases of obese IGT were assigned into an embedding group and a western medication group by random number table, 150 cases in each one. Standardized diagnosis and treatment programs were applied to reduce blood pressure, lipid, weight, and exercise and scientific diet management were used. 0.25 g oral deltamine was prescribed three times a day in the western medication group. Thumb-tack needle for subcutaneous embedding was at bilateral Weiwanxiashu (EX-B 3), Ganshu (BL 18), Pishu (BL 20), Tianshu (ST 25) and Zusanli (ST 36) for 36 to 48 hours on Monday and Thursday, 3 months as a session, with other acupoints differentiated. All the treatment was given for 2 years. The indexes included the blood sugar indexes [fasting plasma glucose (FPG), 2 h postprandial blood glucose (2 h PG), glycosylated hemoglobin (HbA1c)], incidence of hypoglycemia, obesity indexes [waist circumference, body mass index (BMI)], blood lipid indexes [serum total cholesterol (TC), serum triacylglycerol (TG), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C)], liver and kidney function indexes [serum creatinine (Scr), blood urea nitrogen (BUN) and blood uric acid (UA), glutamic-pyruvic transaminase (ALT)] and TCM symptom score. The effects and the incidence of type 2 diabetes were evaluated. Results: After treatment, 2 h PG and HbA1c reduced in the two groups (P0.05). After treatment, waist circumference and BMI reduced in the two groups (both P0.05). Scr, BUN, UA and ALT before and after treatment in the two groups had no statistical difference (all P>0.05), without statistical difference after treatment between the two groups (all P>0.05). The TCM score after treatment was lower than that before treatment in the embedding group (P0.05). The different value of TCM score in the embedding group was better than that in the western medication group (P<0.01). The total effective rate in the embedding group was 98.0% (147/150), which was superior to 92.7% (139/150) in the western medication group (P<0.05). The incidence of type 2 diabetes was 2.0% (3/150) in the embedding group, and that was better than 7.3% (11/150) in the western medication group (P<0.05). Conclusion: Thumb-tack needle for subcutaneous embedding for 2 years could apparent improve the indexes of IGT, which is better than western medication, without liver and kidney damage.

Many antibiotics, including the macrolides, inhibit protein synthesis by binding to ribosomes. Only some of the macrolides affect the peptidyl transferase reaction. The 16-member ring macrolide antibiotics carbomycin, spiramycin, and tylosin inhibit peptidyl transferase. All these have a disaccharide at position 5 in the lactone ring with a mycarose moiety. We have investigated the functional role of this mycarose moiety. The 14-member ring macrolide erythromycin and the 16-member ring macrolides desmycosin and chalcomycin do not inhibit the peptidyl transferase reaction. These drugs have a monosaccharide at position 5 in the lactone ring. The presence of mycarose was correlated with inhibition of peptidyl transferase, footprints on 23 S rRNA and whether the macrolide can compete with binding of hygromycin A to the ribosome. The binding sites of the macrolides to Escherichia coli ribosomes were investigated by chemical probing of domains II and V of 23 S rRNA. The common binding site is around position A2058, while effects on U2506 depend on the presence of the mycarose sugar. Also, protection at position A752 indicates that a mycinose moiety at position 14 in 16-member ring macrolides interact with hairpin 35 in domain II. Competitive footprinting of ribosomal binding of hygromycin A and macrolides showed that tylosin and spiramycin reduce the hygromycin A protections of nucleotides in 23 S rRNA and that carbomycin abolishes its binding. In contrast, the macrolides that do not inhibit the peptidyl transferase reaction bind to the ribosomes concurrently with hygromycin A. Data are presented to argue that a disaccharide at position 5 in the lactone ring of macrolides is essential for inhibition of peptide bond formation and that the mycarose moiety is placed near the conserved U2506 in the central loop region of domain V 23 S rRNA.