Isolation and characterization of lipid-associated and neurosecretory polypeptides
Author: Stark, Margareta
Date: 2000-06-09
Location: Samuelssonsalen, Scheelelaboratoriet, Tomtebodavägen 6, Karolinska Institutet
Time: 13.30
Department: Institutionen för medicinsk biokemi och biofysik (MBB) / Department of Medical Biochemistry and Biophysics
Abstract
Lipid-interacting proteins play important roles in all living organisms.
This thesis focuses on isolation and characterization of an enzyme in the
triacylglycerol biosynthesis (phosphatidic acid phosphatase, PAP),
hydrophobic polypeptides in bile, and polypeptides in cerebrospinal
fluid. These fields constitute methodological challenges and mean
development of suitable tools in between lipid and protein biochemistry.
Two methods used to measure PAP activity were compared. It was
established that the discrepancy between the methods was mainly due to
different acyl chains of the substrate.
In purification of PAP from the yeast Saccharomyces cerevisiae, an
apparent molecular weight of 35 and/or 40 kDa (determined by SDS-PAGE)
and approximately 67 kDa (determined by size exclusion chromatography)
was obtained. The discrepancy in molecular size indicates that PAP forms
a multimeric structure. The results suggest a smaller subunit size than
previously deduced.
A method to determine protein content in extremely lipid-rich samples
(90-98% lipids), where the protein content is low (1-5%), was developed.
By derivatization of hydrolysed samples to their phenylisothiocarbamyl
forms, and subsequent separation by reversed-phase HPLC, the amino acid
content was determined. In addition, phosphatidylethanolamine and
phosphatidylserine could be detected together with the amino acid
constituents.
A method to isolate polypeptides from lipid-rich material was evaluated.
Separation by cromatography of chloroform/methanol extracts of lipid-rich
tissues as spinal cord, lung and bile on Lipidex-5000 in the solvent
system methanol/ethylene chloride, the polypeptides were well separated
from the majority of the lipids.
Several hydrophobic polypeptides in human gallbladder bile were
identified, as ATP-synthase lipid-binding protein 9, a fragment of
monocyte differentiation antigen CD14, and a fragment of
mac25/insulin-like growth factor-binding protein 7, all not previously
identified in bile.
Several novel proteolytic fragments of neuroendocrine proteins were
identified in human cerebrospinal fluid. Proteolytically processed
fragments of chromogranin A, chromogranin B, neuroendocrine protein 7B2,
proenkephalin, neuroendocrine specific protin VGF, osteopontin, testican
and IGF-II E-peptide were characterized, several of them not previously
reported.
List of papers:
I. Stark M, Humble E (1996). "Difficulties in the assay of phosphatidate phosphohydrolase activity. Influence of ionic strength, detergent, and selection of substrate" Lipids 31(10): 1097-1102
Pubmed
II. Stark M, Humble E, Jörnvall H, Björkhem I (1998). "Phosphatidate phosphatase--a key enzyme in glycerolipid biosynthesis. Studies on the yeast enzyme" J Protein Chem 17(1): 1-7
Pubmed
III. Stark M, Wang Y, Danielsson O, Jörnvall H, Johansson J (1998). "Determination of proteins, phosphatidylethanolamine, and phosphatidylserine in organic solvent extracts of tissue material by analysis of phenylthiocarbamyl derivatives" Anal Biochem 265(1): 97-102
Pubmed
IV. Stark M, Jörnvall H, Johansson J (1999). "Isolation and characterization of hydrophobic polypeptides in human bile" Eur J Biochem 266(1): 209-214
Pubmed
V. Stark M, Danielsson O, Griffiths WJ, Jörnvall H, Johansson J (2000). "The peptide repertoire of human cerebrospinal fluid: novel proteolytic fragments of neuroendocrine proteins" (Submitted)
I. Stark M, Humble E (1996). "Difficulties in the assay of phosphatidate phosphohydrolase activity. Influence of ionic strength, detergent, and selection of substrate" Lipids 31(10): 1097-1102
Pubmed
II. Stark M, Humble E, Jörnvall H, Björkhem I (1998). "Phosphatidate phosphatase--a key enzyme in glycerolipid biosynthesis. Studies on the yeast enzyme" J Protein Chem 17(1): 1-7
Pubmed
III. Stark M, Wang Y, Danielsson O, Jörnvall H, Johansson J (1998). "Determination of proteins, phosphatidylethanolamine, and phosphatidylserine in organic solvent extracts of tissue material by analysis of phenylthiocarbamyl derivatives" Anal Biochem 265(1): 97-102
Pubmed
IV. Stark M, Jörnvall H, Johansson J (1999). "Isolation and characterization of hydrophobic polypeptides in human bile" Eur J Biochem 266(1): 209-214
Pubmed
V. Stark M, Danielsson O, Griffiths WJ, Jörnvall H, Johansson J (2000). "The peptide repertoire of human cerebrospinal fluid: novel proteolytic fragments of neuroendocrine proteins" (Submitted)
Issue date: 2000-05-19
Publication year: 2000
ISBN: 91-628-4202-1
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