title: Effect of pH on Cleavage of Glycogen by Vaginal Enzymes.
abstract: Glycogen expressed by the lower genital tract epithelium is believed to support Lactobacillus growth in vivo, although most genital isolates of Lactobacillus are not able to use glycogen as an energy source in vitro. We recently reported that α-amylase is present in the genital fluid of women and that it breaks down glycogen into small carbohydrates that support growth of lactobacilli. Since the pH of the lower genital tract can be very low, we determined how low pH affects glycogen processing by α-amylase. α-amylase in saliva degraded glycogen similarly at pH 6 and 7, but activity was reduced by 52% at pH 4. The glycogen degrading activity in nine genital samples from seven women showed a similar profile with an average reduction of more than 50% at pH 4. However, two samples collected from one woman at different times had a strikingly different pH profile with increased glycogen degradation at pH 4, 5 and 6 compared to pH 7. This second pH profile did not correlate with levels of human α-acid glucosidase or human intestinal maltase glucoamylase. High-performance anion-exchange chromatography showed that mostly maltose was produced from glycogen by samples with the second pH profile in contrast to genital α-amylase that yielded maltose, maltotriose and maltotetraose. These studies show that at low pH, α-amylase activity is reduced to low but detectable levels, which we speculate helps maintain Lactobacillus growth at a limited but sustained rate. Additionally, some women have a genital enzyme distinct from α-amylase with higher activity at low pH. Further studies are needed to determine the identity and distribution of this second enzyme, and whether its presence influences the makeup of genital microbiota.
authors.affiliation: Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America.
authors.forename: Greg T
authors.initials: GT
authors.lastname: Spear
authors.affiliation: Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America.
authors.forename: Mary
authors.initials: M
authors.lastname: McKenna
authors.affiliation: Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America.
authors.forename: Alan L
authors.initials: AL
authors.lastname: Landay
authors.affiliation: Department of Immunology/Microbiology, Rush University Medical Center, Chicago, Illinois, United States of America.
authors.forename: Hadijat
authors.initials: H
authors.lastname: Makinde
authors.affiliation: Whistler Center for Carbohydrate Research, Department of Food Science, Purdue University, West Lafayette, Indiana, United States of America.
authors.forename: Bruce
authors.initials: B
authors.lastname: Hamaker
authors.affiliation: CORE Center of Cook County Health and Hospitals System, Department of Medicine, Rush University Medical Center, Chicago, Illinois, United States of America.
authors.forename: Audrey L
authors.initials: AL
authors.lastname: French
authors.affiliation: Department of Food Science and Biotechnology, College of BioNano Technology, Gachon University, Seongnam, Korea.
authors.forename: Byung-Hoo
authors.initials: BH
authors.lastname: Lee
mesh_terms: D000328:Adult; D005260:Female; D006003:Glycogen / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D064307:Microbiota; D008875:Middle Aged; D012463:Saliva / Q000201:enzymology; D014621:Vagina / Q000737:chemistry* / Q000201:enzymology* / Q000382:microbiology; D000516:alpha-Amylases / Q000378:metabolism
chemical_list: D006003:Glycogen; D000516:alpha-Amylases